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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Git User Manual</title><link rel="stylesheet" type="text/css" href="docbook-xsl.css"><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div lang="en" class="book"><div class="titlepage"><div><div><h1 class="title"><a name="idp6464305424"></a>Git User Manual</h1></div></div><hr></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="preface"><a href="#idp6465409824"></a></span></dt><dt><span class="part"><a href="#repositories-and-branches">I. Repositories and Branches</a></span></dt><dd><dl><dt><span class="chapter"><a href="#how-to-get-a-git-repository">1. How to get a Git repository</a></span></dt><dt><span class="chapter"><a href="#how-to-check-out">2. How to check out a different version of a project</a></span></dt><dt><span class="chapter"><a href="#understanding-commits">3. Understanding History: Commits</a></span></dt><dd><dl><dt><span class="section"><a href="#understanding-reachability">Understanding history: commits, parents, and reachability</a></span></dt><dt><span class="section"><a href="#history-diagrams">Understanding history: History diagrams</a></span></dt><dt><span class="section"><a href="#what-is-a-branch">Understanding history: What is a branch?</a></span></dt></dl></dd><dt><span class="chapter"><a href="#manipulating-branches">4. Manipulating branches</a></span></dt><dt><span class="chapter"><a href="#detached-head">5. Examining an old version without creating a new branch</a></span></dt><dt><span class="chapter"><a href="#examining-remote-branches">6. Examining branches from a remote repository</a></span></dt><dt><span class="chapter"><a href="#how-git-stores-references">7. Naming branches, tags, and other references</a></span></dt><dt><span class="chapter"><a href="#Updating-a-repository-With-git-fetch">8. Updating a repository with git fetch</a></span></dt><dt><span class="chapter"><a href="#fetching-branches">9. Fetching branches from other repositories</a></span></dt></dl></dd><dt><span class="part"><a href="#exploring-git-history">II. Exploring Git history</a></span></dt><dd><dl><dt><span class="chapter"><a href="#using-bisect">10. How to use bisect to find a regression</a></span></dt><dt><span class="chapter"><a href="#naming-commits">11. Naming commits</a></span></dt><dt><span class="chapter"><a href="#creating-tags">12. Creating tags</a></span></dt><dt><span class="chapter"><a href="#browsing-revisions">13. Browsing revisions</a></span></dt><dt><span class="chapter"><a href="#generating-diffs">14. Generating diffs</a></span></dt><dt><span class="chapter"><a href="#viewing-old-file-versions">15. Viewing old file versions</a></span></dt><dt><span class="chapter"><a href="#history-examples">16. Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#counting-commits-on-a-branch">Counting the number of commits on a branch</a></span></dt><dt><span class="section"><a href="#checking-for-equal-branches">Check whether two branches point at the same history</a></span></dt><dt><span class="section"><a href="#finding-tagged-descendants">Find first tagged version including a given fix</a></span></dt><dt><span class="section"><a href="#showing-commits-unique-to-a-branch">Showing commits unique to a given branch</a></span></dt><dt><span class="section"><a href="#making-a-release">Creating a changelog and tarball for a software release</a></span></dt><dt><span class="section"><a href="#Finding-commits-With-given-Content">Finding commits referencing a file with given content</a></span></dt></dl></dd></dl></dd><dt><span class="part"><a href="#Developing-With-git">III. Developing with Git</a></span></dt><dd><dl><dt><span class="chapter"><a href="#telling-git-your-name">17. Telling Git your name</a></span></dt><dt><span class="chapter"><a href="#creating-a-new-repository">18. Creating a new repository</a></span></dt><dt><span class="chapter"><a href="#how-to-make-a-commit">19. How to make a commit</a></span></dt><dt><span class="chapter"><a href="#creating-good-commit-messages">20. Creating good commit messages</a></span></dt><dt><span class="chapter"><a href="#ignoring-files">21. Ignoring files</a></span></dt><dt><span class="chapter"><a href="#how-to-merge">22. How to merge</a></span></dt><dt><span class="chapter"><a href="#resolving-a-merge">23. Resolving a merge</a></span></dt><dd><dl><dt><span class="section"><a href="#conflict-resolution">Getting conflict-resolution help during a merge</a></span></dt></dl></dd><dt><span class="chapter"><a href="#undoing-a-merge">24. Undoing a merge</a></span></dt><dt><span class="chapter"><a href="#fast-forwards">25. Fast-forward merges</a></span></dt><dt><span class="chapter"><a href="#fixing-mistakes">26. Fixing mistakes</a></span></dt><dd><dl><dt><span class="section"><a href="#reverting-a-commit">Fixing a mistake with a new commit</a></span></dt><dt><span class="section"><a href="#fixing-a-mistake-by-rewriting-history">Fixing a mistake by rewriting history</a></span></dt><dt><span class="section"><a href="#checkout-of-path">Checking out an old version of a file</a></span></dt><dt><span class="section"><a href="#interrupted-work">Temporarily setting aside work in progress</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ensuring-good-performance">27. Ensuring good performance</a></span></dt><dt><span class="chapter"><a href="#ensuring-reliability">28. Ensuring reliability</a></span></dt><dd><dl><dt><span class="section"><a href="#checking-for-corruption">Checking the repository for corruption</a></span></dt><dt><span class="section"><a href="#recovering-lost-changes">Recovering lost changes</a></span></dt><dd><dl><dt><span class="section"><a href="#reflogs">Reflogs</a></span></dt><dt><span class="section"><a href="#dangling-object-recovery">Examining dangling objects</a></span></dt></dl></dd></dl></dd></dl></dd><dt><span class="part"><a href="#sharing-development">IV. Sharing development with others</a></span></dt><dd><dl><dt><span class="chapter"><a href="#getting-updates-With-git-pull">29. Getting updates with git pull</a></span></dt><dt><span class="chapter"><a href="#submitting-patches">30. Submitting patches to a project</a></span></dt><dt><span class="chapter"><a href="#importing-patches">31. Importing patches to a project</a></span></dt><dt><span class="chapter"><a href="#public-repositories">32. Public Git repositories</a></span></dt><dd><dl><dt><span class="section"><a href="#setting-up-a-public-repository">Setting up a public repository</a></span></dt><dt><span class="section"><a href="#exporting-via-git">Exporting a Git repository via the Git protocol</a></span></dt><dt><span class="section"><a href="#exporting-via-http">Exporting a git repository via HTTP</a></span></dt><dt><span class="section"><a href="#pushing-changes-to-a-public-repository">Pushing changes to a public repository</a></span></dt><dt><span class="section"><a href="#forcing-push">What to do when a push fails</a></span></dt><dt><span class="section"><a href="#setting-up-a-shared-repository">Setting up a shared repository</a></span></dt><dt><span class="section"><a href="#setting-up-gitweb">Allowing web browsing of a repository</a></span></dt></dl></dd><dt><span class="chapter"><a href="#how-to-get-a-git-repository-with-minimal-history">33. How to get a Git repository with minimal history</a></span></dt><dt><span class="chapter"><a href="#sharing-development-examples">34. Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#maintaining-topic-branches">Maintaining topic branches for a Linux subsystem maintainer</a></span></dt></dl></dd></dl></dd><dt><span class="part"><a href="#cleaning-up-history">V. Rewriting history and maintaining patch series</a></span></dt><dd><dl><dt><span class="chapter"><a href="#patch-series">35. Creating the perfect patch series</a></span></dt><dt><span class="chapter"><a href="#using-git-rebase">36. Keeping a patch series up to date using git rebase</a></span></dt><dt><span class="chapter"><a href="#rewriting-one-commit">37. Rewriting a single commit</a></span></dt><dt><span class="chapter"><a href="#reordering-patch-series">38. Reordering or selecting from a patch series</a></span></dt><dt><span class="chapter"><a href="#interactive-rebase">39. Using interactive rebases</a></span></dt><dt><span class="chapter"><a href="#patch-series-tools">40. Other tools</a></span></dt><dt><span class="chapter"><a href="#problems-With-rewriting-history">41. Problems with rewriting history</a></span></dt><dt><span class="chapter"><a href="#bisect-merges">42. Why bisecting merge commits can be harder than bisecting linear history</a></span></dt></dl></dd><dt><span class="part"><a href="#advanced-branch-management">VI. Advanced branch management</a></span></dt><dd><dl><dt><span class="chapter"><a href="#fetching-individual-branches">43. Fetching individual branches</a></span></dt><dt><span class="chapter"><a href="#fetch-fast-forwards">44. git fetch and fast-forwards</a></span></dt><dt><span class="chapter"><a href="#forcing-fetch">45. Forcing git fetch to do non-fast-forward updates</a></span></dt><dt><span class="chapter"><a href="#remote-branch-configuration">46. Configuring remote-tracking branches</a></span></dt></dl></dd><dt><span class="part"><a href="#git-concepts">VII. Git concepts</a></span></dt><dd><dl><dt><span class="chapter"><a href="#the-object-database">47. The Object Database</a></span></dt><dd><dl><dt><span class="section"><a href="#commit-object">Commit Object</a></span></dt><dt><span class="section"><a href="#tree-object">Tree Object</a></span></dt><dt><span class="section"><a href="#blob-object">Blob Object</a></span></dt><dt><span class="section"><a href="#trust">Trust</a></span></dt><dt><span class="section"><a href="#tag-object">Tag Object</a></span></dt><dt><span class="section"><a href="#pack-files">How Git stores objects efficiently: pack files</a></span></dt><dt><span class="section"><a href="#dangling-objects">Dangling objects</a></span></dt><dt><span class="section"><a href="#recovering-from-repository-corruption">Recovering from repository corruption</a></span></dt></dl></dd><dt><span class="chapter"><a href="#the-index">48. The index</a></span></dt></dl></dd><dt><span class="part"><a href="#submodules">VIII. Submodules</a></span></dt><dd><dl><dt><span class="chapter"><a href="#_pitfalls_with_submodules">49. Pitfalls with submodules</a></span></dt></dl></dd><dt><span class="part"><a href="#low-level-operations">IX. Low-level Git operations</a></span></dt><dd><dl><dt><span class="chapter"><a href="#object-manipulation">50. Object access and manipulation</a></span></dt><dt><span class="chapter"><a href="#the-workflow">51. The Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#working-directory-to-index">working directory → index</a></span></dt><dt><span class="section"><a href="#index-to-object-database">index → object database</a></span></dt><dt><span class="section"><a href="#object-database-to-index">object database → index</a></span></dt><dt><span class="section"><a href="#index-to-working-directory">index → working directory</a></span></dt><dt><span class="section"><a href="#tying-it-all-together">Tying it all together</a></span></dt></dl></dd><dt><span class="chapter"><a href="#examining-the-data">52. Examining the data</a></span></dt><dt><span class="chapter"><a href="#merging-multiple-trees">53. Merging multiple trees</a></span></dt><dt><span class="chapter"><a href="#merging-multiple-trees-2">54. Merging multiple trees, continued</a></span></dt></dl></dd><dt><span class="part"><a href="#hacking-git">X. Hacking Git</a></span></dt><dd><dl><dt><span class="chapter"><a href="#object-details">55. Object storage format</a></span></dt><dt><span class="chapter"><a href="#birdview-on-the-source-code">56. A birds-eye view of Git’s source code</a></span></dt></dl></dd><dt><span class="part"><a href="#glossary">XI. Git Glossary</a></span></dt><dd><dl><dt><span class="chapter"><a href="#git-explained">57. Git explained</a></span></dt></dl></dd><dt><span class="part"><a href="#git-quick-start">XII. Appendix A: Git Quick Reference</a></span></dt><dd><dl><dt><span class="chapter"><a href="#quick-creating-a-new-repository">58. Creating a new repository</a></span></dt><dt><span class="chapter"><a href="#managing-branches">59. Managing branches</a></span></dt><dt><span class="chapter"><a href="#exploring-history">60. Exploring history</a></span></dt><dt><span class="chapter"><a href="#making-changes">61. Making changes</a></span></dt><dt><span class="chapter"><a href="#merging">62. Merging</a></span></dt><dt><span class="chapter"><a href="#sharing-your-changes">63. Sharing your changes</a></span></dt><dt><span class="chapter"><a href="#repository-maintenance">64. Repository maintenance</a></span></dt></dl></dd><dt><span class="part"><a href="#todo">XIII. Appendix B: Notes and todo list for this manual</a></span></dt><dd><dl><dt><span class="chapter"><a href="#todo-list">65. Todo list</a></span></dt></dl></dd></dl></div><div class="preface"><div class="titlepage"><div><div><h1 class="title"><a name="idp6465409824"></a></h1></div></div></div><p>Git is a fast distributed revision control system.</p><p>This manual is designed to be readable by someone with basic UNIX
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command-line skills, but no previous knowledge of Git.</p><p><a class="xref" href="#repositories-and-branches" title="Part I. Repositories and Branches">Part I, “Repositories and Branches”</a> and <a class="xref" href="#exploring-git-history" title="Part II. Exploring Git history">Part II, “Exploring Git history”</a> explain how
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to fetch and study a project using git—read these chapters to learn how
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to build and test a particular version of a software project, search for
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regressions, and so on.</p><p>People needing to do actual development will also want to read
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<a class="xref" href="#Developing-With-git" title="Part III. Developing with Git">Part III, “Developing with Git”</a> and <a class="xref" href="#sharing-development" title="Part IV. Sharing development with others">Part IV, “Sharing development with others”</a>.</p><p>Further chapters cover more specialized topics.</p><p>Comprehensive reference documentation is available through the man
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pages, or git-help(1) command. For example, for the command
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<code class="literal">git clone <repo></code>, you can either use:</p><pre class="screen">$ man git-clone</pre><p>or:</p><pre class="screen">$ git help clone</pre><p>With the latter, you can use the manual viewer of your choice; see
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git-help(1) for more information.</p><p>See also <a class="xref" href="#git-quick-start" title="Part XII. Appendix A: Git Quick Reference">Part XII, “Appendix A: Git Quick Reference”</a> for a brief overview of Git commands,
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without any explanation.</p><p>Finally, see <a class="xref" href="#todo" title="Part XIII. Appendix B: Notes and todo list for this manual">Part XIII, “Appendix B: Notes and todo list for this manual”</a> for ways that you can help make this manual more
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complete.</p></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="repositories-and-branches"></a>Part I. Repositories and Branches</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#how-to-get-a-git-repository">1. How to get a Git repository</a></span></dt><dt><span class="chapter"><a href="#how-to-check-out">2. How to check out a different version of a project</a></span></dt><dt><span class="chapter"><a href="#understanding-commits">3. Understanding History: Commits</a></span></dt><dd><dl><dt><span class="section"><a href="#understanding-reachability">Understanding history: commits, parents, and reachability</a></span></dt><dt><span class="section"><a href="#history-diagrams">Understanding history: History diagrams</a></span></dt><dt><span class="section"><a href="#what-is-a-branch">Understanding history: What is a branch?</a></span></dt></dl></dd><dt><span class="chapter"><a href="#manipulating-branches">4. Manipulating branches</a></span></dt><dt><span class="chapter"><a href="#detached-head">5. Examining an old version without creating a new branch</a></span></dt><dt><span class="chapter"><a href="#examining-remote-branches">6. Examining branches from a remote repository</a></span></dt><dt><span class="chapter"><a href="#how-git-stores-references">7. Naming branches, tags, and other references</a></span></dt><dt><span class="chapter"><a href="#Updating-a-repository-With-git-fetch">8. Updating a repository with git fetch</a></span></dt><dt><span class="chapter"><a href="#fetching-branches">9. Fetching branches from other repositories</a></span></dt></dl></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="how-to-get-a-git-repository"></a>Chapter 1. How to get a Git repository</h2></div></div></div><p>It will be useful to have a Git repository to experiment with as you
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read this manual.</p><p>The best way to get one is by using the git-clone(1) command to
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download a copy of an existing repository. If you don’t already have a
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project in mind, here are some interesting examples:</p><pre class="screen"> # Git itself (approx. 40MB download):
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$ git clone git://git.kernel.org/pub/scm/git/git.git
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# the Linux kernel (approx. 640MB download):
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$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git</pre><p>The initial clone may be time-consuming for a large project, but you
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will only need to clone once.</p><p>The clone command creates a new directory named after the project
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(<code class="literal">git</code> or <code class="literal">linux</code> in the examples above). After you cd into this
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directory, you will see that it contains a copy of the project files,
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called the <a class="link" href="#def_working_tree">working tree</a>, together with a special
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top-level directory named <code class="literal">.git</code>, which contains all the information
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about the history of the project.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="how-to-check-out"></a>Chapter 2. How to check out a different version of a project</h2></div></div></div><p>Git is best thought of as a tool for storing the history of a collection
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of files. It stores the history as a compressed collection of
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interrelated snapshots of the project’s contents. In Git each such
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version is called a <a class="link" href="#def_commit">commit</a>.</p><p>Those snapshots aren’t necessarily all arranged in a single line from
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oldest to newest; instead, work may simultaneously proceed along
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parallel lines of development, called <a class="link" href="#def_branch">branches</a>, which may
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merge and diverge.</p><p>A single Git repository can track development on multiple branches. It
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does this by keeping a list of <a class="link" href="#def_head">heads</a> which reference the
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latest commit on each branch; the git-branch(1) command shows
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you the list of branch heads:</p><pre class="screen">$ git branch
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* master</pre><p>A freshly cloned repository contains a single branch head, by default
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named "master", with the working directory initialized to the state of
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the project referred to by that branch head.</p><p>Most projects also use <a class="link" href="#def_tag">tags</a>. Tags, like heads, are
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references into the project’s history, and can be listed using the
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git-tag(1) command:</p><pre class="screen">$ git tag -l
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v2.6.11
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v2.6.11-tree
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v2.6.12
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v2.6.12-rc2
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v2.6.12-rc3
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v2.6.12-rc4
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v2.6.12-rc5
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v2.6.12-rc6
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v2.6.13
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...</pre><p>Tags are expected to always point at the same version of a project,
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while heads are expected to advance as development progresses.</p><p>Create a new branch head pointing to one of these versions and check it
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out using git-checkout(1):</p><pre class="screen">$ git checkout -b new v2.6.13</pre><p>The working directory then reflects the contents that the project had
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when it was tagged v2.6.13, and git-branch(1) shows two
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branches, with an asterisk marking the currently checked-out branch:</p><pre class="screen">$ git branch
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master
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* new</pre><p>If you decide that you’d rather see version 2.6.17, you can modify
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the current branch to point at v2.6.17 instead, with</p><pre class="screen">$ git reset --hard v2.6.17</pre><p>Note that if the current branch head was your only reference to a
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particular point in history, then resetting that branch may leave you
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with no way to find the history it used to point to; so use this command
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carefully.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="understanding-commits"></a>Chapter 3. Understanding History: Commits</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#understanding-reachability">Understanding history: commits, parents, and reachability</a></span></dt><dt><span class="section"><a href="#history-diagrams">Understanding history: History diagrams</a></span></dt><dt><span class="section"><a href="#what-is-a-branch">Understanding history: What is a branch?</a></span></dt></dl></div><p>Every change in the history of a project is represented by a commit.
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The git-show(1) command shows the most recent commit on the
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current branch:</p><pre class="screen">$ git show
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commit 17cf781661e6d38f737f15f53ab552f1e95960d7
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Author: Linus Torvalds <torvalds@ppc970.osdl.org.(none)>
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Date: Tue Apr 19 14:11:06 2005 -0700
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Remove duplicate getenv(DB_ENVIRONMENT) call
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Noted by Tony Luck.
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diff --git a/init-db.c b/init-db.c
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index 65898fa..b002dc6 100644
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--- a/init-db.c
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+++ b/init-db.c
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@@ -7,7 +7,7 @@
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int main(int argc, char **argv)
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{
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- char *sha1_dir = getenv(DB_ENVIRONMENT), *path;
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+ char *sha1_dir, *path;
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int len, i;
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if (mkdir(".git", 0755) < 0) {</pre><p>As you can see, a commit shows who made the latest change, what they
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did, and why.</p><p>Every commit has a 40-hexdigit id, sometimes called the "object name" or the
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"SHA-1 id", shown on the first line of the <code class="literal">git show</code> output. You can usually
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refer to a commit by a shorter name, such as a tag or a branch name, but this
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longer name can also be useful. Most importantly, it is a globally unique
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name for this commit: so if you tell somebody else the object name (for
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example in email), then you are guaranteed that name will refer to the same
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commit in their repository that it does in yours (assuming their repository
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has that commit at all). Since the object name is computed as a hash over the
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contents of the commit, you are guaranteed that the commit can never change
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without its name also changing.</p><p>In fact, in <a class="xref" href="#git-concepts" title="Part VII. Git concepts">Part VII, “Git concepts”</a> we shall see that everything stored in Git
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||
history, including file data and directory contents, is stored in an object
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||
with a name that is a hash of its contents.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="understanding-reachability"></a>Understanding history: commits, parents, and reachability</h2></div></div></div><p>Every commit (except the very first commit in a project) also has a
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||
parent commit which shows what happened before this commit.
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||
Following the chain of parents will eventually take you back to the
|
||
beginning of the project.</p><p>However, the commits do not form a simple list; Git allows lines of
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||
development to diverge and then reconverge, and the point where two
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||
lines of development reconverge is called a "merge". The commit
|
||
representing a merge can therefore have more than one parent, with
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||
each parent representing the most recent commit on one of the lines
|
||
of development leading to that point.</p><p>The best way to see how this works is using the gitk(1)
|
||
command; running gitk now on a Git repository and looking for merge
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||
commits will help understand how Git organizes history.</p><p>In the following, we say that commit X is "reachable" from commit Y
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||
if commit X is an ancestor of commit Y. Equivalently, you could say
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||
that Y is a descendant of X, or that there is a chain of parents
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||
leading from commit Y to commit X.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="history-diagrams"></a>Understanding history: History diagrams</h2></div></div></div><p>We will sometimes represent Git history using diagrams like the one
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||
below. Commits are shown as "o", and the links between them with
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||
lines drawn with - / and \. Time goes left to right:</p><pre class="literallayout"> o--o--o <-- Branch A
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||
/
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||
o--o--o <-- master
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||
\
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||
o--o--o <-- Branch B</pre><p>If we need to talk about a particular commit, the character "o" may
|
||
be replaced with another letter or number.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="what-is-a-branch"></a>Understanding history: What is a branch?</h2></div></div></div><p>When we need to be precise, we will use the word "branch" to mean a line
|
||
of development, and "branch head" (or just "head") to mean a reference
|
||
to the most recent commit on a branch. In the example above, the branch
|
||
head named "A" is a pointer to one particular commit, but we refer to
|
||
the line of three commits leading up to that point as all being part of
|
||
"branch A".</p><p>However, when no confusion will result, we often just use the term
|
||
"branch" both for branches and for branch heads.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="manipulating-branches"></a>Chapter 4. Manipulating branches</h2></div></div></div><p>Creating, deleting, and modifying branches is quick and easy; here’s
|
||
a summary of the commands:</p><div class="variablelist"><dl class="variablelist"><dt><span class="term"><code class="literal">git branch</code></span></dt><dd>list all branches.</dd><dt><span class="term"><code class="literal">git branch <branch></code></span></dt><dd>create a new branch named <code class="literal"><branch></code>, referencing the same
|
||
point in history as the current branch.</dd><dt><span class="term"><code class="literal">git branch <branch> <start-point></code></span></dt><dd>create a new branch named <code class="literal"><branch></code>, referencing
|
||
<code class="literal"><start-point></code>, which may be specified any way you like,
|
||
including using a branch name or a tag name.</dd><dt><span class="term"><code class="literal">git branch -d <branch></code></span></dt><dd>delete the branch <code class="literal"><branch></code>; if the branch is not fully
|
||
merged in its upstream branch or contained in the current branch,
|
||
this command will fail with a warning.</dd><dt><span class="term"><code class="literal">git branch -D <branch></code></span></dt><dd>delete the branch <code class="literal"><branch></code> irrespective of its merged status.</dd><dt><span class="term"><code class="literal">git checkout <branch></code></span></dt><dd>make the current branch <code class="literal"><branch></code>, updating the working
|
||
directory to reflect the version referenced by <code class="literal"><branch></code>.</dd><dt><span class="term"><code class="literal">git checkout -b <new> <start-point></code></span></dt><dd>create a new branch <code class="literal"><new></code> referencing <code class="literal"><start-point></code>, and
|
||
check it out.</dd></dl></div><p>The special symbol "HEAD" can always be used to refer to the current
|
||
branch. In fact, Git uses a file named <code class="literal">HEAD</code> in the <code class="literal">.git</code> directory
|
||
to remember which branch is current:</p><pre class="screen">$ cat .git/HEAD
|
||
ref: refs/heads/master</pre></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="detached-head"></a>Chapter 5. Examining an old version without creating a new branch</h2></div></div></div><p>The <code class="literal">git checkout</code> command normally expects a branch head, but will also
|
||
accept an arbitrary commit; for example, you can check out the commit
|
||
referenced by a tag:</p><pre class="screen">$ git checkout v2.6.17
|
||
Note: checking out 'v2.6.17'.
|
||
|
||
You are in 'detached HEAD' state. You can look around, make experimental
|
||
changes and commit them, and you can discard any commits you make in this
|
||
state without impacting any branches by performing another checkout.
|
||
|
||
If you want to create a new branch to retain commits you create, you may
|
||
do so (now or later) by using -b with the checkout command again. Example:
|
||
|
||
git checkout -b new_branch_name
|
||
|
||
HEAD is now at 427abfa Linux v2.6.17</pre><p>The HEAD then refers to the SHA-1 of the commit instead of to a branch,
|
||
and git branch shows that you are no longer on a branch:</p><pre class="screen">$ cat .git/HEAD
|
||
427abfa28afedffadfca9dd8b067eb6d36bac53f
|
||
$ git branch
|
||
* (detached from v2.6.17)
|
||
master</pre><p>In this case we say that the HEAD is "detached".</p><p>This is an easy way to check out a particular version without having to
|
||
make up a name for the new branch. You can still create a new branch
|
||
(or tag) for this version later if you decide to.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="examining-remote-branches"></a>Chapter 6. Examining branches from a remote repository</h2></div></div></div><p>The "master" branch that was created at the time you cloned is a copy
|
||
of the HEAD in the repository that you cloned from. That repository
|
||
may also have had other branches, though, and your local repository
|
||
keeps branches which track each of those remote branches, called
|
||
remote-tracking branches, which you
|
||
can view using the <code class="literal">-r</code> option to git-branch(1):</p><pre class="screen">$ git branch -r
|
||
origin/HEAD
|
||
origin/html
|
||
origin/maint
|
||
origin/man
|
||
origin/master
|
||
origin/next
|
||
origin/pu
|
||
origin/todo</pre><p>In this example, "origin" is called a remote repository, or "remote"
|
||
for short. The branches of this repository are called "remote
|
||
branches" from our point of view. The remote-tracking branches listed
|
||
above were created based on the remote branches at clone time and will
|
||
be updated by <code class="literal">git fetch</code> (hence <code class="literal">git pull</code>) and <code class="literal">git push</code>. See
|
||
<a class="xref" href="#Updating-a-repository-With-git-fetch" title="Chapter 8. Updating a repository with git fetch">Chapter 8, <i>Updating a repository with git fetch</i></a> for details.</p><p>You might want to build on one of these remote-tracking branches
|
||
on a branch of your own, just as you would for a tag:</p><pre class="screen">$ git checkout -b my-todo-copy origin/todo</pre><p>You can also check out <code class="literal">origin/todo</code> directly to examine it or
|
||
write a one-off patch. See <a class="link" href="#detached-head" title="Chapter 5. Examining an old version without creating a new branch">detached head</a>.</p><p>Note that the name "origin" is just the name that Git uses by default
|
||
to refer to the repository that you cloned from.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="how-git-stores-references"></a>Chapter 7. Naming branches, tags, and other references</h2></div></div></div><p>Branches, remote-tracking branches, and tags are all references to
|
||
commits. All references are named with a slash-separated path name
|
||
starting with <code class="literal">refs</code>; the names we’ve been using so far are actually
|
||
shorthand:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">The branch <code class="literal">test</code> is short for <code class="literal">refs/heads/test</code>.</li><li class="listitem">The tag <code class="literal">v2.6.18</code> is short for <code class="literal">refs/tags/v2.6.18</code>.</li><li class="listitem"><code class="literal">origin/master</code> is short for <code class="literal">refs/remotes/origin/master</code>.</li></ul></div><p>The full name is occasionally useful if, for example, there ever
|
||
exists a tag and a branch with the same name.</p><p>(Newly created refs are actually stored in the <code class="literal">.git/refs</code> directory,
|
||
under the path given by their name. However, for efficiency reasons
|
||
they may also be packed together in a single file; see
|
||
git-pack-refs(1)).</p><p>As another useful shortcut, the "HEAD" of a repository can be referred
|
||
to just using the name of that repository. So, for example, "origin"
|
||
is usually a shortcut for the HEAD branch in the repository "origin".</p><p>For the complete list of paths which Git checks for references, and
|
||
the order it uses to decide which to choose when there are multiple
|
||
references with the same shorthand name, see the "SPECIFYING
|
||
REVISIONS" section of gitrevisions(7).</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="Updating-a-repository-With-git-fetch"></a>Chapter 8. Updating a repository with git fetch</h2></div></div></div><p>After you clone a repository and commit a few changes of your own, you
|
||
may wish to check the original repository for updates.</p><p>The <code class="literal">git-fetch</code> command, with no arguments, will update all of the
|
||
remote-tracking branches to the latest version found in the original
|
||
repository. It will not touch any of your own branches—not even the
|
||
"master" branch that was created for you on clone.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="fetching-branches"></a>Chapter 9. Fetching branches from other repositories</h2></div></div></div><p>You can also track branches from repositories other than the one you
|
||
cloned from, using git-remote(1):</p><pre class="screen">$ git remote add staging git://git.kernel.org/.../gregkh/staging.git
|
||
$ git fetch staging
|
||
...
|
||
From git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging
|
||
* [new branch] master -> staging/master
|
||
* [new branch] staging-linus -> staging/staging-linus
|
||
* [new branch] staging-next -> staging/staging-next</pre><p>New remote-tracking branches will be stored under the shorthand name
|
||
that you gave <code class="literal">git remote add</code>, in this case <code class="literal">staging</code>:</p><pre class="screen">$ git branch -r
|
||
origin/HEAD -> origin/master
|
||
origin/master
|
||
staging/master
|
||
staging/staging-linus
|
||
staging/staging-next</pre><p>If you run <code class="literal">git fetch <remote></code> later, the remote-tracking branches
|
||
for the named <code class="literal"><remote></code> will be updated.</p><p>If you examine the file <code class="literal">.git/config</code>, you will see that Git has added
|
||
a new stanza:</p><pre class="screen">$ cat .git/config
|
||
...
|
||
[remote "staging"]
|
||
url = git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
|
||
fetch = +refs/heads/*:refs/remotes/staging/*
|
||
...</pre><p>This is what causes Git to track the remote’s branches; you may modify
|
||
or delete these configuration options by editing <code class="literal">.git/config</code> with a
|
||
text editor. (See the "CONFIGURATION FILE" section of
|
||
git-config(1) for details.)</p></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="exploring-git-history"></a>Part II. Exploring Git history</h1></div></div></div><div class="partintro"><div></div><p>Git is best thought of as a tool for storing the history of a
|
||
collection of files. It does this by storing compressed snapshots of
|
||
the contents of a file hierarchy, together with "commits" which show
|
||
the relationships between these snapshots.</p><p>Git provides extremely flexible and fast tools for exploring the
|
||
history of a project.</p><p>We start with one specialized tool that is useful for finding the
|
||
commit that introduced a bug into a project.</p><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#using-bisect">10. How to use bisect to find a regression</a></span></dt><dt><span class="chapter"><a href="#naming-commits">11. Naming commits</a></span></dt><dt><span class="chapter"><a href="#creating-tags">12. Creating tags</a></span></dt><dt><span class="chapter"><a href="#browsing-revisions">13. Browsing revisions</a></span></dt><dt><span class="chapter"><a href="#generating-diffs">14. Generating diffs</a></span></dt><dt><span class="chapter"><a href="#viewing-old-file-versions">15. Viewing old file versions</a></span></dt><dt><span class="chapter"><a href="#history-examples">16. Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#counting-commits-on-a-branch">Counting the number of commits on a branch</a></span></dt><dt><span class="section"><a href="#checking-for-equal-branches">Check whether two branches point at the same history</a></span></dt><dt><span class="section"><a href="#finding-tagged-descendants">Find first tagged version including a given fix</a></span></dt><dt><span class="section"><a href="#showing-commits-unique-to-a-branch">Showing commits unique to a given branch</a></span></dt><dt><span class="section"><a href="#making-a-release">Creating a changelog and tarball for a software release</a></span></dt><dt><span class="section"><a href="#Finding-commits-With-given-Content">Finding commits referencing a file with given content</a></span></dt></dl></dd></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="using-bisect"></a>Chapter 10. How to use bisect to find a regression</h2></div></div></div><p>Suppose version 2.6.18 of your project worked, but the version at
|
||
"master" crashes. Sometimes the best way to find the cause of such a
|
||
regression is to perform a brute-force search through the project’s
|
||
history to find the particular commit that caused the problem. The
|
||
git-bisect(1) command can help you do this:</p><pre class="screen">$ git bisect start
|
||
$ git bisect good v2.6.18
|
||
$ git bisect bad master
|
||
Bisecting: 3537 revisions left to test after this
|
||
[65934a9a028b88e83e2b0f8b36618fe503349f8e] BLOCK: Make USB storage depend on SCSI rather than selecting it [try #6]</pre><p>If you run <code class="literal">git branch</code> at this point, you’ll see that Git has
|
||
temporarily moved you in "(no branch)". HEAD is now detached from any
|
||
branch and points directly to a commit (with commit id 65934) that
|
||
is reachable from "master" but not from v2.6.18. Compile and test it,
|
||
and see whether it crashes. Assume it does crash. Then:</p><pre class="screen">$ git bisect bad
|
||
Bisecting: 1769 revisions left to test after this
|
||
[7eff82c8b1511017ae605f0c99ac275a7e21b867] i2c-core: Drop useless bitmaskings</pre><p>checks out an older version. Continue like this, telling Git at each
|
||
stage whether the version it gives you is good or bad, and notice
|
||
that the number of revisions left to test is cut approximately in
|
||
half each time.</p><p>After about 13 tests (in this case), it will output the commit id of
|
||
the guilty commit. You can then examine the commit with
|
||
git-show(1), find out who wrote it, and mail them your bug
|
||
report with the commit id. Finally, run</p><pre class="screen">$ git bisect reset</pre><p>to return you to the branch you were on before.</p><p>Note that the version which <code class="literal">git bisect</code> checks out for you at each
|
||
point is just a suggestion, and you’re free to try a different
|
||
version if you think it would be a good idea. For example,
|
||
occasionally you may land on a commit that broke something unrelated;
|
||
run</p><pre class="screen">$ git bisect visualize</pre><p>which will run gitk and label the commit it chose with a marker that
|
||
says "bisect". Choose a safe-looking commit nearby, note its commit
|
||
id, and check it out with:</p><pre class="screen">$ git reset --hard fb47ddb2db</pre><p>then test, run <code class="literal">bisect good</code> or <code class="literal">bisect bad</code> as appropriate, and
|
||
continue.</p><p>Instead of <code class="literal">git bisect visualize</code> and then <code class="literal">git reset --hard
|
||
fb47ddb2db</code>, you might just want to tell Git that you want to skip
|
||
the current commit:</p><pre class="screen">$ git bisect skip</pre><p>In this case, though, Git may not eventually be able to tell the first
|
||
bad one between some first skipped commits and a later bad commit.</p><p>There are also ways to automate the bisecting process if you have a
|
||
test script that can tell a good from a bad commit. See
|
||
git-bisect(1) for more information about this and other <code class="literal">git
|
||
bisect</code> features.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="naming-commits"></a>Chapter 11. Naming commits</h2></div></div></div><p>We have seen several ways of naming commits already:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">40-hexdigit object name</li><li class="listitem">branch name: refers to the commit at the head of the given
|
||
branch</li><li class="listitem">tag name: refers to the commit pointed to by the given tag
|
||
(we’ve seen branches and tags are special cases of
|
||
<a class="link" href="#how-git-stores-references" title="Chapter 7. Naming branches, tags, and other references">references</a>).</li><li class="listitem">HEAD: refers to the head of the current branch</li></ul></div><p>There are many more; see the "SPECIFYING REVISIONS" section of the
|
||
gitrevisions(7) man page for the complete list of ways to
|
||
name revisions. Some examples:</p><pre class="screen">$ git show fb47ddb2 # the first few characters of the object name
|
||
# are usually enough to specify it uniquely
|
||
$ git show HEAD^ # the parent of the HEAD commit
|
||
$ git show HEAD^^ # the grandparent
|
||
$ git show HEAD~4 # the great-great-grandparent</pre><p>Recall that merge commits may have more than one parent; by default,
|
||
<code class="literal">^</code> and <code class="literal">~</code> follow the first parent listed in the commit, but you can
|
||
also choose:</p><pre class="screen">$ git show HEAD^1 # show the first parent of HEAD
|
||
$ git show HEAD^2 # show the second parent of HEAD</pre><p>In addition to HEAD, there are several other special names for
|
||
commits:</p><p>Merges (to be discussed later), as well as operations such as
|
||
<code class="literal">git reset</code>, which change the currently checked-out commit, generally
|
||
set ORIG_HEAD to the value HEAD had before the current operation.</p><p>The <code class="literal">git fetch</code> operation always stores the head of the last fetched
|
||
branch in FETCH_HEAD. For example, if you run <code class="literal">git fetch</code> without
|
||
specifying a local branch as the target of the operation</p><pre class="screen">$ git fetch git://example.com/proj.git theirbranch</pre><p>the fetched commits will still be available from FETCH_HEAD.</p><p>When we discuss merges we’ll also see the special name MERGE_HEAD,
|
||
which refers to the other branch that we’re merging in to the current
|
||
branch.</p><p>The git-rev-parse(1) command is a low-level command that is
|
||
occasionally useful for translating some name for a commit to the object
|
||
name for that commit:</p><pre class="screen">$ git rev-parse origin
|
||
e05db0fd4f31dde7005f075a84f96b360d05984b</pre></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="creating-tags"></a>Chapter 12. Creating tags</h2></div></div></div><p>We can also create a tag to refer to a particular commit; after
|
||
running</p><pre class="screen">$ git tag stable-1 1b2e1d63ff</pre><p>You can use <code class="literal">stable-1</code> to refer to the commit 1b2e1d63ff.</p><p>This creates a "lightweight" tag. If you would also like to include a
|
||
comment with the tag, and possibly sign it cryptographically, then you
|
||
should create a tag object instead; see the git-tag(1) man page
|
||
for details.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="browsing-revisions"></a>Chapter 13. Browsing revisions</h2></div></div></div><p>The git-log(1) command can show lists of commits. On its
|
||
own, it shows all commits reachable from the parent commit; but you
|
||
can also make more specific requests:</p><pre class="screen">$ git log v2.5.. # commits since (not reachable from) v2.5
|
||
$ git log test..master # commits reachable from master but not test
|
||
$ git log master..test # ...reachable from test but not master
|
||
$ git log master...test # ...reachable from either test or master,
|
||
# but not both
|
||
$ git log --since="2 weeks ago" # commits from the last 2 weeks
|
||
$ git log Makefile # commits which modify Makefile
|
||
$ git log fs/ # ... which modify any file under fs/
|
||
$ git log -S'foo()' # commits which add or remove any file data
|
||
# matching the string 'foo()'</pre><p>And of course you can combine all of these; the following finds
|
||
commits since v2.5 which touch the <code class="literal">Makefile</code> or any file under <code class="literal">fs</code>:</p><pre class="screen">$ git log v2.5.. Makefile fs/</pre><p>You can also ask git log to show patches:</p><pre class="screen">$ git log -p</pre><p>See the <code class="literal">--pretty</code> option in the git-log(1) man page for more
|
||
display options.</p><p>Note that git log starts with the most recent commit and works
|
||
backwards through the parents; however, since Git history can contain
|
||
multiple independent lines of development, the particular order that
|
||
commits are listed in may be somewhat arbitrary.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="generating-diffs"></a>Chapter 14. Generating diffs</h2></div></div></div><p>You can generate diffs between any two versions using
|
||
git-diff(1):</p><pre class="screen">$ git diff master..test</pre><p>That will produce the diff between the tips of the two branches. If
|
||
you’d prefer to find the diff from their common ancestor to test, you
|
||
can use three dots instead of two:</p><pre class="screen">$ git diff master...test</pre><p>Sometimes what you want instead is a set of patches; for this you can
|
||
use git-format-patch(1):</p><pre class="screen">$ git format-patch master..test</pre><p>will generate a file with a patch for each commit reachable from test
|
||
but not from master.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="viewing-old-file-versions"></a>Chapter 15. Viewing old file versions</h2></div></div></div><p>You can always view an old version of a file by just checking out the
|
||
correct revision first. But sometimes it is more convenient to be
|
||
able to view an old version of a single file without checking
|
||
anything out; this command does that:</p><pre class="screen">$ git show v2.5:fs/locks.c</pre><p>Before the colon may be anything that names a commit, and after it
|
||
may be any path to a file tracked by Git.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="history-examples"></a>Chapter 16. Examples</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#counting-commits-on-a-branch">Counting the number of commits on a branch</a></span></dt><dt><span class="section"><a href="#checking-for-equal-branches">Check whether two branches point at the same history</a></span></dt><dt><span class="section"><a href="#finding-tagged-descendants">Find first tagged version including a given fix</a></span></dt><dt><span class="section"><a href="#showing-commits-unique-to-a-branch">Showing commits unique to a given branch</a></span></dt><dt><span class="section"><a href="#making-a-release">Creating a changelog and tarball for a software release</a></span></dt><dt><span class="section"><a href="#Finding-commits-With-given-Content">Finding commits referencing a file with given content</a></span></dt></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="counting-commits-on-a-branch"></a>Counting the number of commits on a branch</h2></div></div></div><p>Suppose you want to know how many commits you’ve made on <code class="literal">mybranch</code>
|
||
since it diverged from <code class="literal">origin</code>:</p><pre class="screen">$ git log --pretty=oneline origin..mybranch | wc -l</pre><p>Alternatively, you may often see this sort of thing done with the
|
||
lower-level command git-rev-list(1), which just lists the SHA-1’s
|
||
of all the given commits:</p><pre class="screen">$ git rev-list origin..mybranch | wc -l</pre></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="checking-for-equal-branches"></a>Check whether two branches point at the same history</h2></div></div></div><p>Suppose you want to check whether two branches point at the same point
|
||
in history.</p><pre class="screen">$ git diff origin..master</pre><p>will tell you whether the contents of the project are the same at the
|
||
two branches; in theory, however, it’s possible that the same project
|
||
contents could have been arrived at by two different historical
|
||
routes. You could compare the object names:</p><pre class="screen">$ git rev-list origin
|
||
e05db0fd4f31dde7005f075a84f96b360d05984b
|
||
$ git rev-list master
|
||
e05db0fd4f31dde7005f075a84f96b360d05984b</pre><p>Or you could recall that the <code class="literal">...</code> operator selects all commits
|
||
reachable from either one reference or the other but not
|
||
both; so</p><pre class="screen">$ git log origin...master</pre><p>will return no commits when the two branches are equal.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="finding-tagged-descendants"></a>Find first tagged version including a given fix</h2></div></div></div><p>Suppose you know that the commit e05db0fd fixed a certain problem.
|
||
You’d like to find the earliest tagged release that contains that
|
||
fix.</p><p>Of course, there may be more than one answer—if the history branched
|
||
after commit e05db0fd, then there could be multiple "earliest" tagged
|
||
releases.</p><p>You could just visually inspect the commits since e05db0fd:</p><pre class="screen">$ gitk e05db0fd..</pre><p>or you can use git-name-rev(1), which will give the commit a
|
||
name based on any tag it finds pointing to one of the commit’s
|
||
descendants:</p><pre class="screen">$ git name-rev --tags e05db0fd
|
||
e05db0fd tags/v1.5.0-rc1^0~23</pre><p>The git-describe(1) command does the opposite, naming the
|
||
revision using a tag on which the given commit is based:</p><pre class="screen">$ git describe e05db0fd
|
||
v1.5.0-rc0-260-ge05db0f</pre><p>but that may sometimes help you guess which tags might come after the
|
||
given commit.</p><p>If you just want to verify whether a given tagged version contains a
|
||
given commit, you could use git-merge-base(1):</p><pre class="screen">$ git merge-base e05db0fd v1.5.0-rc1
|
||
e05db0fd4f31dde7005f075a84f96b360d05984b</pre><p>The merge-base command finds a common ancestor of the given commits,
|
||
and always returns one or the other in the case where one is a
|
||
descendant of the other; so the above output shows that e05db0fd
|
||
actually is an ancestor of v1.5.0-rc1.</p><p>Alternatively, note that</p><pre class="screen">$ git log v1.5.0-rc1..e05db0fd</pre><p>will produce empty output if and only if v1.5.0-rc1 includes e05db0fd,
|
||
because it outputs only commits that are not reachable from v1.5.0-rc1.</p><p>As yet another alternative, the git-show-branch(1) command lists
|
||
the commits reachable from its arguments with a display on the left-hand
|
||
side that indicates which arguments that commit is reachable from.
|
||
So, if you run something like</p><pre class="screen">$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2
|
||
! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
|
||
available
|
||
! [v1.5.0-rc0] GIT v1.5.0 preview
|
||
! [v1.5.0-rc1] GIT v1.5.0-rc1
|
||
! [v1.5.0-rc2] GIT v1.5.0-rc2
|
||
...</pre><p>then a line like</p><pre class="screen">+ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if
|
||
available</pre><p>shows that e05db0fd is reachable from itself, from v1.5.0-rc1,
|
||
and from v1.5.0-rc2, and not from v1.5.0-rc0.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="showing-commits-unique-to-a-branch"></a>Showing commits unique to a given branch</h2></div></div></div><p>Suppose you would like to see all the commits reachable from the branch
|
||
head named <code class="literal">master</code> but not from any other head in your repository.</p><p>We can list all the heads in this repository with
|
||
git-show-ref(1):</p><pre class="screen">$ git show-ref --heads
|
||
bf62196b5e363d73353a9dcf094c59595f3153b7 refs/heads/core-tutorial
|
||
db768d5504c1bb46f63ee9d6e1772bd047e05bf9 refs/heads/maint
|
||
a07157ac624b2524a059a3414e99f6f44bebc1e7 refs/heads/master
|
||
24dbc180ea14dc1aebe09f14c8ecf32010690627 refs/heads/tutorial-2
|
||
1e87486ae06626c2f31eaa63d26fc0fd646c8af2 refs/heads/tutorial-fixes</pre><p>We can get just the branch-head names, and remove <code class="literal">master</code>, with
|
||
the help of the standard utilities cut and grep:</p><pre class="screen">$ git show-ref --heads | cut -d' ' -f2 | grep -v '^refs/heads/master'
|
||
refs/heads/core-tutorial
|
||
refs/heads/maint
|
||
refs/heads/tutorial-2
|
||
refs/heads/tutorial-fixes</pre><p>And then we can ask to see all the commits reachable from master
|
||
but not from these other heads:</p><pre class="screen">$ gitk master --not $( git show-ref --heads | cut -d' ' -f2 |
|
||
grep -v '^refs/heads/master' )</pre><p>Obviously, endless variations are possible; for example, to see all
|
||
commits reachable from some head but not from any tag in the repository:</p><pre class="screen">$ gitk $( git show-ref --heads ) --not $( git show-ref --tags )</pre><p>(See gitrevisions(7) for explanations of commit-selecting
|
||
syntax such as <code class="literal">--not</code>.)</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="making-a-release"></a>Creating a changelog and tarball for a software release</h2></div></div></div><p>The git-archive(1) command can create a tar or zip archive from
|
||
any version of a project; for example:</p><pre class="screen">$ git archive -o latest.tar.gz --prefix=project/ HEAD</pre><p>will use HEAD to produce a gzipped tar archive in which each filename
|
||
is preceded by <code class="literal">project/</code>. The output file format is inferred from
|
||
the output file extension if possible, see git-archive(1) for
|
||
details.</p><p>Versions of Git older than 1.7.7 don’t know about the <code class="literal">tar.gz</code> format,
|
||
you’ll need to use gzip explicitly:</p><pre class="screen">$ git archive --format=tar --prefix=project/ HEAD | gzip >latest.tar.gz</pre><p>If you’re releasing a new version of a software project, you may want
|
||
to simultaneously make a changelog to include in the release
|
||
announcement.</p><p>Linus Torvalds, for example, makes new kernel releases by tagging them,
|
||
then running:</p><pre class="screen">$ release-script 2.6.12 2.6.13-rc6 2.6.13-rc7</pre><p>where release-script is a shell script that looks like:</p><pre class="screen">#!/bin/sh
|
||
stable="$1"
|
||
last="$2"
|
||
new="$3"
|
||
echo "# git tag v$new"
|
||
echo "git archive --prefix=linux-$new/ v$new | gzip -9 > ../linux-$new.tar.gz"
|
||
echo "git diff v$stable v$new | gzip -9 > ../patch-$new.gz"
|
||
echo "git log --no-merges v$new ^v$last > ../ChangeLog-$new"
|
||
echo "git shortlog --no-merges v$new ^v$last > ../ShortLog"
|
||
echo "git diff --stat --summary -M v$last v$new > ../diffstat-$new"</pre><p>and then he just cut-and-pastes the output commands after verifying that
|
||
they look OK.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="Finding-commits-With-given-Content"></a>Finding commits referencing a file with given content</h2></div></div></div><p>Somebody hands you a copy of a file, and asks which commits modified a
|
||
file such that it contained the given content either before or after the
|
||
commit. You can find out with this:</p><pre class="screen">$ git log --raw --abbrev=40 --pretty=oneline |
|
||
grep -B 1 `git hash-object filename`</pre><p>Figuring out why this works is left as an exercise to the (advanced)
|
||
student. The git-log(1), git-diff-tree(1), and
|
||
git-hash-object(1) man pages may prove helpful.</p></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="Developing-With-git"></a>Part III. Developing with Git</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#telling-git-your-name">17. Telling Git your name</a></span></dt><dt><span class="chapter"><a href="#creating-a-new-repository">18. Creating a new repository</a></span></dt><dt><span class="chapter"><a href="#how-to-make-a-commit">19. How to make a commit</a></span></dt><dt><span class="chapter"><a href="#creating-good-commit-messages">20. Creating good commit messages</a></span></dt><dt><span class="chapter"><a href="#ignoring-files">21. Ignoring files</a></span></dt><dt><span class="chapter"><a href="#how-to-merge">22. How to merge</a></span></dt><dt><span class="chapter"><a href="#resolving-a-merge">23. Resolving a merge</a></span></dt><dd><dl><dt><span class="section"><a href="#conflict-resolution">Getting conflict-resolution help during a merge</a></span></dt></dl></dd><dt><span class="chapter"><a href="#undoing-a-merge">24. Undoing a merge</a></span></dt><dt><span class="chapter"><a href="#fast-forwards">25. Fast-forward merges</a></span></dt><dt><span class="chapter"><a href="#fixing-mistakes">26. Fixing mistakes</a></span></dt><dd><dl><dt><span class="section"><a href="#reverting-a-commit">Fixing a mistake with a new commit</a></span></dt><dt><span class="section"><a href="#fixing-a-mistake-by-rewriting-history">Fixing a mistake by rewriting history</a></span></dt><dt><span class="section"><a href="#checkout-of-path">Checking out an old version of a file</a></span></dt><dt><span class="section"><a href="#interrupted-work">Temporarily setting aside work in progress</a></span></dt></dl></dd><dt><span class="chapter"><a href="#ensuring-good-performance">27. Ensuring good performance</a></span></dt><dt><span class="chapter"><a href="#ensuring-reliability">28. Ensuring reliability</a></span></dt><dd><dl><dt><span class="section"><a href="#checking-for-corruption">Checking the repository for corruption</a></span></dt><dt><span class="section"><a href="#recovering-lost-changes">Recovering lost changes</a></span></dt><dd><dl><dt><span class="section"><a href="#reflogs">Reflogs</a></span></dt><dt><span class="section"><a href="#dangling-object-recovery">Examining dangling objects</a></span></dt></dl></dd></dl></dd></dl></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="telling-git-your-name"></a>Chapter 17. Telling Git your name</h2></div></div></div><p>Before creating any commits, you should introduce yourself to Git.
|
||
The easiest way to do so is to use git-config(1):</p><pre class="screen">$ git config --global user.name 'Your Name Comes Here'
|
||
$ git config --global user.email 'you@yourdomain.example.com'</pre><p>Which will add the following to a file named <code class="literal">.gitconfig</code> in your
|
||
home directory:</p><pre class="screen">[user]
|
||
name = Your Name Comes Here
|
||
email = you@yourdomain.example.com</pre><p>See the "CONFIGURATION FILE" section of git-config(1) for
|
||
details on the configuration file. The file is plain text, so you can
|
||
also edit it with your favorite editor.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="creating-a-new-repository"></a>Chapter 18. Creating a new repository</h2></div></div></div><p>Creating a new repository from scratch is very easy:</p><pre class="screen">$ mkdir project
|
||
$ cd project
|
||
$ git init</pre><p>If you have some initial content (say, a tarball):</p><pre class="screen">$ tar xzvf project.tar.gz
|
||
$ cd project
|
||
$ git init
|
||
$ git add . # include everything below ./ in the first commit:
|
||
$ git commit</pre></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="how-to-make-a-commit"></a>Chapter 19. How to make a commit</h2></div></div></div><p>Creating a new commit takes three steps:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">Making some changes to the working directory using your
|
||
favorite editor.</li><li class="listitem">Telling Git about your changes.</li><li class="listitem">Creating the commit using the content you told Git about
|
||
in step 2.</li></ol></div><p>In practice, you can interleave and repeat steps 1 and 2 as many
|
||
times as you want: in order to keep track of what you want committed
|
||
at step 3, Git maintains a snapshot of the tree’s contents in a
|
||
special staging area called "the index."</p><p>At the beginning, the content of the index will be identical to
|
||
that of the HEAD. The command <code class="literal">git diff --cached</code>, which shows
|
||
the difference between the HEAD and the index, should therefore
|
||
produce no output at that point.</p><p>Modifying the index is easy:</p><p>To update the index with the contents of a new or modified file, use</p><pre class="screen">$ git add path/to/file</pre><p>To remove a file from the index and from the working tree, use</p><pre class="screen">$ git rm path/to/file</pre><p>After each step you can verify that</p><pre class="screen">$ git diff --cached</pre><p>always shows the difference between the HEAD and the index file—this
|
||
is what you’d commit if you created the commit now—and that</p><pre class="screen">$ git diff</pre><p>shows the difference between the working tree and the index file.</p><p>Note that <code class="literal">git add</code> always adds just the current contents of a file
|
||
to the index; further changes to the same file will be ignored unless
|
||
you run <code class="literal">git add</code> on the file again.</p><p>When you’re ready, just run</p><pre class="screen">$ git commit</pre><p>and Git will prompt you for a commit message and then create the new
|
||
commit. Check to make sure it looks like what you expected with</p><pre class="screen">$ git show</pre><p>As a special shortcut,</p><pre class="screen">$ git commit -a</pre><p>will update the index with any files that you’ve modified or removed
|
||
and create a commit, all in one step.</p><p>A number of commands are useful for keeping track of what you’re
|
||
about to commit:</p><pre class="screen">$ git diff --cached # difference between HEAD and the index; what
|
||
# would be committed if you ran "commit" now.
|
||
$ git diff # difference between the index file and your
|
||
# working directory; changes that would not
|
||
# be included if you ran "commit" now.
|
||
$ git diff HEAD # difference between HEAD and working tree; what
|
||
# would be committed if you ran "commit -a" now.
|
||
$ git status # a brief per-file summary of the above.</pre><p>You can also use git-gui(1) to create commits, view changes in
|
||
the index and the working tree files, and individually select diff hunks
|
||
for inclusion in the index (by right-clicking on the diff hunk and
|
||
choosing "Stage Hunk For Commit").</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="creating-good-commit-messages"></a>Chapter 20. Creating good commit messages</h2></div></div></div><p>Though not required, it’s a good idea to begin the commit message
|
||
with a single short (less than 50 character) line summarizing the
|
||
change, followed by a blank line and then a more thorough
|
||
description. The text up to the first blank line in a commit
|
||
message is treated as the commit title, and that title is used
|
||
throughout Git. For example, git-format-patch(1) turns a
|
||
commit into email, and it uses the title on the Subject line and the
|
||
rest of the commit in the body.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="ignoring-files"></a>Chapter 21. Ignoring files</h2></div></div></div><p>A project will often generate files that you do <span class="emphasis"><em>not</em></span> want to track with Git.
|
||
This typically includes files generated by a build process or temporary
|
||
backup files made by your editor. Of course, <span class="emphasis"><em>not</em></span> tracking files with Git
|
||
is just a matter of <span class="emphasis"><em>not</em></span> calling <code class="literal">git add</code> on them. But it quickly becomes
|
||
annoying to have these untracked files lying around; e.g. they make
|
||
<code class="literal">git add .</code> practically useless, and they keep showing up in the output of
|
||
<code class="literal">git status</code>.</p><p>You can tell Git to ignore certain files by creating a file called
|
||
<code class="literal">.gitignore</code> in the top level of your working directory, with contents
|
||
such as:</p><pre class="screen"># Lines starting with '#' are considered comments.
|
||
# Ignore any file named foo.txt.
|
||
foo.txt
|
||
# Ignore (generated) html files,
|
||
*.html
|
||
# except foo.html which is maintained by hand.
|
||
!foo.html
|
||
# Ignore objects and archives.
|
||
*.[oa]</pre><p>See gitignore(5) for a detailed explanation of the syntax. You can
|
||
also place .gitignore files in other directories in your working tree, and they
|
||
will apply to those directories and their subdirectories. The <code class="literal">.gitignore</code>
|
||
files can be added to your repository like any other files (just run <code class="literal">git add
|
||
.gitignore</code> and <code class="literal">git commit</code>, as usual), which is convenient when the exclude
|
||
patterns (such as patterns matching build output files) would also make sense
|
||
for other users who clone your repository.</p><p>If you wish the exclude patterns to affect only certain repositories
|
||
(instead of every repository for a given project), you may instead put
|
||
them in a file in your repository named <code class="literal">.git/info/exclude</code>, or in any
|
||
file specified by the <code class="literal">core.excludesFile</code> configuration variable.
|
||
Some Git commands can also take exclude patterns directly on the
|
||
command line. See gitignore(5) for the details.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="how-to-merge"></a>Chapter 22. How to merge</h2></div></div></div><p>You can rejoin two diverging branches of development using
|
||
git-merge(1):</p><pre class="screen">$ git merge branchname</pre><p>merges the development in the branch <code class="literal">branchname</code> into the current
|
||
branch.</p><p>A merge is made by combining the changes made in <code class="literal">branchname</code> and the
|
||
changes made up to the latest commit in your current branch since
|
||
their histories forked. The work tree is overwritten by the result of
|
||
the merge when this combining is done cleanly, or overwritten by a
|
||
half-merged results when this combining results in conflicts.
|
||
Therefore, if you have uncommitted changes touching the same files as
|
||
the ones impacted by the merge, Git will refuse to proceed. Most of
|
||
the time, you will want to commit your changes before you can merge,
|
||
and if you don’t, then git-stash(1) can take these changes
|
||
away while you’re doing the merge, and reapply them afterwards.</p><p>If the changes are independent enough, Git will automatically complete
|
||
the merge and commit the result (or reuse an existing commit in case
|
||
of <a class="link" href="#fast-forwards" title="Chapter 25. Fast-forward merges">fast-forward</a>, see below). On the other hand,
|
||
if there are conflicts—for example, if the same file is
|
||
modified in two different ways in the remote branch and the local
|
||
branch—then you are warned; the output may look something like this:</p><pre class="screen">$ git merge next
|
||
100% (4/4) done
|
||
Auto-merged file.txt
|
||
CONFLICT (content): Merge conflict in file.txt
|
||
Automatic merge failed; fix conflicts and then commit the result.</pre><p>Conflict markers are left in the problematic files, and after
|
||
you resolve the conflicts manually, you can update the index
|
||
with the contents and run Git commit, as you normally would when
|
||
creating a new file.</p><p>If you examine the resulting commit using gitk, you will see that it
|
||
has two parents, one pointing to the top of the current branch, and
|
||
one to the top of the other branch.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="resolving-a-merge"></a>Chapter 23. Resolving a merge</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#conflict-resolution">Getting conflict-resolution help during a merge</a></span></dt></dl></div><p>When a merge isn’t resolved automatically, Git leaves the index and
|
||
the working tree in a special state that gives you all the
|
||
information you need to help resolve the merge.</p><p>Files with conflicts are marked specially in the index, so until you
|
||
resolve the problem and update the index, git-commit(1) will
|
||
fail:</p><pre class="screen">$ git commit
|
||
file.txt: needs merge</pre><p>Also, git-status(1) will list those files as "unmerged", and the
|
||
files with conflicts will have conflict markers added, like this:</p><pre class="screen"><<<<<<< HEAD:file.txt
|
||
Hello world
|
||
=======
|
||
Goodbye
|
||
>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt</pre><p>All you need to do is edit the files to resolve the conflicts, and then</p><pre class="screen">$ git add file.txt
|
||
$ git commit</pre><p>Note that the commit message will already be filled in for you with
|
||
some information about the merge. Normally you can just use this
|
||
default message unchanged, but you may add additional commentary of
|
||
your own if desired.</p><p>The above is all you need to know to resolve a simple merge. But Git
|
||
also provides more information to help resolve conflicts:</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="conflict-resolution"></a>Getting conflict-resolution help during a merge</h2></div></div></div><p>All of the changes that Git was able to merge automatically are
|
||
already added to the index file, so git-diff(1) shows only
|
||
the conflicts. It uses an unusual syntax:</p><pre class="screen">$ git diff
|
||
diff --cc file.txt
|
||
index 802992c,2b60207..0000000
|
||
--- a/file.txt
|
||
+++ b/file.txt
|
||
@@@ -1,1 -1,1 +1,5 @@@
|
||
++<<<<<<< HEAD:file.txt
|
||
+Hello world
|
||
++=======
|
||
+ Goodbye
|
||
++>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt</pre><p>Recall that the commit which will be committed after we resolve this
|
||
conflict will have two parents instead of the usual one: one parent
|
||
will be HEAD, the tip of the current branch; the other will be the
|
||
tip of the other branch, which is stored temporarily in MERGE_HEAD.</p><p>During the merge, the index holds three versions of each file. Each of
|
||
these three "file stages" represents a different version of the file:</p><pre class="screen">$ git show :1:file.txt # the file in a common ancestor of both branches
|
||
$ git show :2:file.txt # the version from HEAD.
|
||
$ git show :3:file.txt # the version from MERGE_HEAD.</pre><p>When you ask git-diff(1) to show the conflicts, it runs a
|
||
three-way diff between the conflicted merge results in the work tree with
|
||
stages 2 and 3 to show only hunks whose contents come from both sides,
|
||
mixed (in other words, when a hunk’s merge results come only from stage 2,
|
||
that part is not conflicting and is not shown. Same for stage 3).</p><p>The diff above shows the differences between the working-tree version of
|
||
file.txt and the stage 2 and stage 3 versions. So instead of preceding
|
||
each line by a single <code class="literal">+</code> or <code class="literal">-</code>, it now uses two columns: the first
|
||
column is used for differences between the first parent and the working
|
||
directory copy, and the second for differences between the second parent
|
||
and the working directory copy. (See the "COMBINED DIFF FORMAT" section
|
||
of git-diff-files(1) for a details of the format.)</p><p>After resolving the conflict in the obvious way (but before updating the
|
||
index), the diff will look like:</p><pre class="screen">$ git diff
|
||
diff --cc file.txt
|
||
index 802992c,2b60207..0000000
|
||
--- a/file.txt
|
||
+++ b/file.txt
|
||
@@@ -1,1 -1,1 +1,1 @@@
|
||
- Hello world
|
||
-Goodbye
|
||
++Goodbye world</pre><p>This shows that our resolved version deleted "Hello world" from the
|
||
first parent, deleted "Goodbye" from the second parent, and added
|
||
"Goodbye world", which was previously absent from both.</p><p>Some special diff options allow diffing the working directory against
|
||
any of these stages:</p><pre class="screen">$ git diff -1 file.txt # diff against stage 1
|
||
$ git diff --base file.txt # same as the above
|
||
$ git diff -2 file.txt # diff against stage 2
|
||
$ git diff --ours file.txt # same as the above
|
||
$ git diff -3 file.txt # diff against stage 3
|
||
$ git diff --theirs file.txt # same as the above.</pre><p>The git-log(1) and gitk(1) commands also provide special help
|
||
for merges:</p><pre class="screen">$ git log --merge
|
||
$ gitk --merge</pre><p>These will display all commits which exist only on HEAD or on
|
||
MERGE_HEAD, and which touch an unmerged file.</p><p>You may also use git-mergetool(1), which lets you merge the
|
||
unmerged files using external tools such as Emacs or kdiff3.</p><p>Each time you resolve the conflicts in a file and update the index:</p><pre class="screen">$ git add file.txt</pre><p>the different stages of that file will be "collapsed", after which
|
||
<code class="literal">git diff</code> will (by default) no longer show diffs for that file.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="undoing-a-merge"></a>Chapter 24. Undoing a merge</h2></div></div></div><p>If you get stuck and decide to just give up and throw the whole mess
|
||
away, you can always return to the pre-merge state with</p><pre class="screen">$ git reset --hard HEAD</pre><p>Or, if you’ve already committed the merge that you want to throw away,</p><pre class="screen">$ git reset --hard ORIG_HEAD</pre><p>However, this last command can be dangerous in some cases—never
|
||
throw away a commit you have already committed if that commit may
|
||
itself have been merged into another branch, as doing so may confuse
|
||
further merges.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="fast-forwards"></a>Chapter 25. Fast-forward merges</h2></div></div></div><p>There is one special case not mentioned above, which is treated
|
||
differently. Normally, a merge results in a merge commit, with two
|
||
parents, one pointing at each of the two lines of development that
|
||
were merged.</p><p>However, if the current branch is an ancestor of the other—so every commit
|
||
present in the current branch is already contained in the other branch—then Git
|
||
just performs a "fast-forward"; the head of the current branch is moved forward
|
||
to point at the head of the merged-in branch, without any new commits being
|
||
created.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="fixing-mistakes"></a>Chapter 26. Fixing mistakes</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#reverting-a-commit">Fixing a mistake with a new commit</a></span></dt><dt><span class="section"><a href="#fixing-a-mistake-by-rewriting-history">Fixing a mistake by rewriting history</a></span></dt><dt><span class="section"><a href="#checkout-of-path">Checking out an old version of a file</a></span></dt><dt><span class="section"><a href="#interrupted-work">Temporarily setting aside work in progress</a></span></dt></dl></div><p>If you’ve messed up the working tree, but haven’t yet committed your
|
||
mistake, you can return the entire working tree to the last committed
|
||
state with</p><pre class="screen">$ git reset --hard HEAD</pre><p>If you make a commit that you later wish you hadn’t, there are two
|
||
fundamentally different ways to fix the problem:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">You can create a new commit that undoes whatever was done
|
||
by the old commit. This is the correct thing if your
|
||
mistake has already been made public.</li><li class="listitem">You can go back and modify the old commit. You should
|
||
never do this if you have already made the history public;
|
||
Git does not normally expect the "history" of a project to
|
||
change, and cannot correctly perform repeated merges from
|
||
a branch that has had its history changed.</li></ol></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="reverting-a-commit"></a>Fixing a mistake with a new commit</h2></div></div></div><p>Creating a new commit that reverts an earlier change is very easy;
|
||
just pass the git-revert(1) command a reference to the bad
|
||
commit; for example, to revert the most recent commit:</p><pre class="screen">$ git revert HEAD</pre><p>This will create a new commit which undoes the change in HEAD. You
|
||
will be given a chance to edit the commit message for the new commit.</p><p>You can also revert an earlier change, for example, the next-to-last:</p><pre class="screen">$ git revert HEAD^</pre><p>In this case Git will attempt to undo the old change while leaving
|
||
intact any changes made since then. If more recent changes overlap
|
||
with the changes to be reverted, then you will be asked to fix
|
||
conflicts manually, just as in the case of <a class="link" href="#resolving-a-merge" title="Chapter 23. Resolving a merge">resolving a merge</a>.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="fixing-a-mistake-by-rewriting-history"></a>Fixing a mistake by rewriting history</h2></div></div></div><p>If the problematic commit is the most recent commit, and you have not
|
||
yet made that commit public, then you may just
|
||
<a class="link" href="#undoing-a-merge" title="Chapter 24. Undoing a merge">destroy it using <code class="literal">git reset</code></a>.</p><p>Alternatively, you
|
||
can edit the working directory and update the index to fix your
|
||
mistake, just as if you were going to <a class="link" href="#how-to-make-a-commit" title="Chapter 19. How to make a commit">create a
|
||
new commit</a>, then run</p><pre class="screen">$ git commit --amend</pre><p>which will replace the old commit by a new commit incorporating your
|
||
changes, giving you a chance to edit the old commit message first.</p><p>Again, you should never do this to a commit that may already have
|
||
been merged into another branch; use git-revert(1) instead in
|
||
that case.</p><p>It is also possible to replace commits further back in the history, but
|
||
this is an advanced topic to be left for
|
||
<a class="link" href="#cleaning-up-history" title="Part V. Rewriting history and maintaining patch series">another chapter</a>.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="checkout-of-path"></a>Checking out an old version of a file</h2></div></div></div><p>In the process of undoing a previous bad change, you may find it
|
||
useful to check out an older version of a particular file using
|
||
git-checkout(1). We’ve used <code class="literal">git checkout</code> before to switch
|
||
branches, but it has quite different behavior if it is given a path
|
||
name: the command</p><pre class="screen">$ git checkout HEAD^ path/to/file</pre><p>replaces path/to/file by the contents it had in the commit HEAD^, and
|
||
also updates the index to match. It does not change branches.</p><p>If you just want to look at an old version of the file, without
|
||
modifying the working directory, you can do that with
|
||
git-show(1):</p><pre class="screen">$ git show HEAD^:path/to/file</pre><p>which will display the given version of the file.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="interrupted-work"></a>Temporarily setting aside work in progress</h2></div></div></div><p>While you are in the middle of working on something complicated, you
|
||
find an unrelated but obvious and trivial bug. You would like to fix it
|
||
before continuing. You can use git-stash(1) to save the current
|
||
state of your work, and after fixing the bug (or, optionally after doing
|
||
so on a different branch and then coming back), unstash the
|
||
work-in-progress changes.</p><pre class="screen">$ git stash push -m "work in progress for foo feature"</pre><p>This command will save your changes away to the <code class="literal">stash</code>, and
|
||
reset your working tree and the index to match the tip of your
|
||
current branch. Then you can make your fix as usual.</p><pre class="screen">... edit and test ...
|
||
$ git commit -a -m "blorpl: typofix"</pre><p>After that, you can go back to what you were working on with
|
||
<code class="literal">git stash pop</code>:</p><pre class="screen">$ git stash pop</pre></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="ensuring-good-performance"></a>Chapter 27. Ensuring good performance</h2></div></div></div><p>On large repositories, Git depends on compression to keep the history
|
||
information from taking up too much space on disk or in memory. Some
|
||
Git commands may automatically run git-gc(1), so you don’t
|
||
have to worry about running it manually. However, compressing a large
|
||
repository may take a while, so you may want to call <code class="literal">gc</code> explicitly
|
||
to avoid automatic compression kicking in when it is not convenient.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="ensuring-reliability"></a>Chapter 28. Ensuring reliability</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#checking-for-corruption">Checking the repository for corruption</a></span></dt><dt><span class="section"><a href="#recovering-lost-changes">Recovering lost changes</a></span></dt><dd><dl><dt><span class="section"><a href="#reflogs">Reflogs</a></span></dt><dt><span class="section"><a href="#dangling-object-recovery">Examining dangling objects</a></span></dt></dl></dd></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="checking-for-corruption"></a>Checking the repository for corruption</h2></div></div></div><p>The git-fsck(1) command runs a number of self-consistency checks
|
||
on the repository, and reports on any problems. This may take some
|
||
time.</p><pre class="screen">$ git fsck
|
||
dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
|
||
dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
|
||
dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
|
||
dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb
|
||
dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f
|
||
dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e
|
||
dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085
|
||
dangling tree b24c2473f1fd3d91352a624795be026d64c8841f
|
||
...</pre><p>You will see informational messages on dangling objects. They are objects
|
||
that still exist in the repository but are no longer referenced by any of
|
||
your branches, and can (and will) be removed after a while with <code class="literal">gc</code>.
|
||
You can run <code class="literal">git fsck --no-dangling</code> to suppress these messages, and still
|
||
view real errors.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="recovering-lost-changes"></a>Recovering lost changes</h2></div></div></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="reflogs"></a>Reflogs</h3></div></div></div><p>Say you modify a branch with <a class="link" href="#fixing-mistakes" title="Chapter 26. Fixing mistakes"><code class="literal">git reset --hard</code></a>,
|
||
and then realize that the branch was the only reference you had to
|
||
that point in history.</p><p>Fortunately, Git also keeps a log, called a "reflog", of all the
|
||
previous values of each branch. So in this case you can still find the
|
||
old history using, for example,</p><pre class="screen">$ git log master@{1}</pre><p>This lists the commits reachable from the previous version of the
|
||
<code class="literal">master</code> branch head. This syntax can be used with any Git command
|
||
that accepts a commit, not just with <code class="literal">git log</code>. Some other examples:</p><pre class="screen">$ git show master@{2} # See where the branch pointed 2,
|
||
$ git show master@{3} # 3, ... changes ago.
|
||
$ gitk master@{yesterday} # See where it pointed yesterday,
|
||
$ gitk master@{"1 week ago"} # ... or last week
|
||
$ git log --walk-reflogs master # show reflog entries for master</pre><p>A separate reflog is kept for the HEAD, so</p><pre class="screen">$ git show HEAD@{"1 week ago"}</pre><p>will show what HEAD pointed to one week ago, not what the current branch
|
||
pointed to one week ago. This allows you to see the history of what
|
||
you’ve checked out.</p><p>The reflogs are kept by default for 30 days, after which they may be
|
||
pruned. See git-reflog(1) and git-gc(1) to learn
|
||
how to control this pruning, and see the "SPECIFYING REVISIONS"
|
||
section of gitrevisions(7) for details.</p><p>Note that the reflog history is very different from normal Git history.
|
||
While normal history is shared by every repository that works on the
|
||
same project, the reflog history is not shared: it tells you only about
|
||
how the branches in your local repository have changed over time.</p></div><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="dangling-object-recovery"></a>Examining dangling objects</h3></div></div></div><p>In some situations the reflog may not be able to save you. For example,
|
||
suppose you delete a branch, then realize you need the history it
|
||
contained. The reflog is also deleted; however, if you have not yet
|
||
pruned the repository, then you may still be able to find the lost
|
||
commits in the dangling objects that <code class="literal">git fsck</code> reports. See
|
||
<a class="xref" href="#dangling-objects" title="Dangling objects">the section called “Dangling objects”</a> for the details.</p><pre class="screen">$ git fsck
|
||
dangling commit 7281251ddd2a61e38657c827739c57015671a6b3
|
||
dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63
|
||
dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5
|
||
...</pre><p>You can examine
|
||
one of those dangling commits with, for example,</p><pre class="screen">$ gitk 7281251ddd --not --all</pre><p>which does what it sounds like: it says that you want to see the commit
|
||
history that is described by the dangling commit(s), but not the
|
||
history that is described by all your existing branches and tags. Thus
|
||
you get exactly the history reachable from that commit that is lost.
|
||
(And notice that it might not be just one commit: we only report the
|
||
"tip of the line" as being dangling, but there might be a whole deep
|
||
and complex commit history that was dropped.)</p><p>If you decide you want the history back, you can always create a new
|
||
reference pointing to it, for example, a new branch:</p><pre class="screen">$ git branch recovered-branch 7281251ddd</pre><p>Other types of dangling objects (blobs and trees) are also possible, and
|
||
dangling objects can arise in other situations.</p></div></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="sharing-development"></a>Part IV. Sharing development with others</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#getting-updates-With-git-pull">29. Getting updates with git pull</a></span></dt><dt><span class="chapter"><a href="#submitting-patches">30. Submitting patches to a project</a></span></dt><dt><span class="chapter"><a href="#importing-patches">31. Importing patches to a project</a></span></dt><dt><span class="chapter"><a href="#public-repositories">32. Public Git repositories</a></span></dt><dd><dl><dt><span class="section"><a href="#setting-up-a-public-repository">Setting up a public repository</a></span></dt><dt><span class="section"><a href="#exporting-via-git">Exporting a Git repository via the Git protocol</a></span></dt><dt><span class="section"><a href="#exporting-via-http">Exporting a git repository via HTTP</a></span></dt><dt><span class="section"><a href="#pushing-changes-to-a-public-repository">Pushing changes to a public repository</a></span></dt><dt><span class="section"><a href="#forcing-push">What to do when a push fails</a></span></dt><dt><span class="section"><a href="#setting-up-a-shared-repository">Setting up a shared repository</a></span></dt><dt><span class="section"><a href="#setting-up-gitweb">Allowing web browsing of a repository</a></span></dt></dl></dd><dt><span class="chapter"><a href="#how-to-get-a-git-repository-with-minimal-history">33. How to get a Git repository with minimal history</a></span></dt><dt><span class="chapter"><a href="#sharing-development-examples">34. Examples</a></span></dt><dd><dl><dt><span class="section"><a href="#maintaining-topic-branches">Maintaining topic branches for a Linux subsystem maintainer</a></span></dt></dl></dd></dl></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="getting-updates-With-git-pull"></a>Chapter 29. Getting updates with git pull</h2></div></div></div><p>After you clone a repository and commit a few changes of your own, you
|
||
may wish to check the original repository for updates and merge them
|
||
into your own work.</p><p>We have already seen <a class="link" href="#Updating-a-repository-With-git-fetch" title="Chapter 8. Updating a repository with git fetch">how to
|
||
keep remote-tracking branches up to date</a> with git-fetch(1),
|
||
and how to merge two branches. So you can merge in changes from the
|
||
original repository’s master branch with:</p><pre class="screen">$ git fetch
|
||
$ git merge origin/master</pre><p>However, the git-pull(1) command provides a way to do this in
|
||
one step:</p><pre class="screen">$ git pull origin master</pre><p>In fact, if you have <code class="literal">master</code> checked out, then this branch has been
|
||
configured by <code class="literal">git clone</code> to get changes from the HEAD branch of the
|
||
origin repository. So often you can
|
||
accomplish the above with just a simple</p><pre class="screen">$ git pull</pre><p>This command will fetch changes from the remote branches to your
|
||
remote-tracking branches <code class="literal">origin/*</code>, and merge the default branch into
|
||
the current branch.</p><p>More generally, a branch that is created from a remote-tracking branch
|
||
will pull
|
||
by default from that branch. See the descriptions of the
|
||
<code class="literal">branch.<name>.remote</code> and <code class="literal">branch.<name>.merge</code> options in
|
||
git-config(1), and the discussion of the <code class="literal">--track</code> option in
|
||
git-checkout(1), to learn how to control these defaults.</p><p>In addition to saving you keystrokes, <code class="literal">git pull</code> also helps you by
|
||
producing a default commit message documenting the branch and
|
||
repository that you pulled from.</p><p>(But note that no such commit will be created in the case of a
|
||
<a class="link" href="#fast-forwards" title="Chapter 25. Fast-forward merges">fast-forward</a>; instead, your branch will just be
|
||
updated to point to the latest commit from the upstream branch.)</p><p>The <code class="literal">git pull</code> command can also be given <code class="literal">.</code> as the "remote" repository,
|
||
in which case it just merges in a branch from the current repository; so
|
||
the commands</p><pre class="screen">$ git pull . branch
|
||
$ git merge branch</pre><p>are roughly equivalent.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="submitting-patches"></a>Chapter 30. Submitting patches to a project</h2></div></div></div><p>If you just have a few changes, the simplest way to submit them may
|
||
just be to send them as patches in email:</p><p>First, use git-format-patch(1); for example:</p><pre class="screen">$ git format-patch origin</pre><p>will produce a numbered series of files in the current directory, one
|
||
for each patch in the current branch but not in <code class="literal">origin/HEAD</code>.</p><p><code class="literal">git format-patch</code> can include an initial "cover letter". You can insert
|
||
commentary on individual patches after the three dash line which
|
||
<code class="literal">format-patch</code> places after the commit message but before the patch
|
||
itself. If you use <code class="literal">git notes</code> to track your cover letter material,
|
||
<code class="literal">git format-patch --notes</code> will include the commit’s notes in a similar
|
||
manner.</p><p>You can then import these into your mail client and send them by
|
||
hand. However, if you have a lot to send at once, you may prefer to
|
||
use the git-send-email(1) script to automate the process.
|
||
Consult the mailing list for your project first to determine
|
||
their requirements for submitting patches.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="importing-patches"></a>Chapter 31. Importing patches to a project</h2></div></div></div><p>Git also provides a tool called git-am(1) (am stands for
|
||
"apply mailbox"), for importing such an emailed series of patches.
|
||
Just save all of the patch-containing messages, in order, into a
|
||
single mailbox file, say <code class="literal">patches.mbox</code>, then run</p><pre class="screen">$ git am -3 patches.mbox</pre><p>Git will apply each patch in order; if any conflicts are found, it
|
||
will stop, and you can fix the conflicts as described in
|
||
"<a class="link" href="#resolving-a-merge" title="Chapter 23. Resolving a merge">Resolving a merge</a>". (The <code class="literal">-3</code> option tells
|
||
Git to perform a merge; if you would prefer it just to abort and
|
||
leave your tree and index untouched, you may omit that option.)</p><p>Once the index is updated with the results of the conflict
|
||
resolution, instead of creating a new commit, just run</p><pre class="screen">$ git am --continue</pre><p>and Git will create the commit for you and continue applying the
|
||
remaining patches from the mailbox.</p><p>The final result will be a series of commits, one for each patch in
|
||
the original mailbox, with authorship and commit log message each
|
||
taken from the message containing each patch.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="public-repositories"></a>Chapter 32. Public Git repositories</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#setting-up-a-public-repository">Setting up a public repository</a></span></dt><dt><span class="section"><a href="#exporting-via-git">Exporting a Git repository via the Git protocol</a></span></dt><dt><span class="section"><a href="#exporting-via-http">Exporting a git repository via HTTP</a></span></dt><dt><span class="section"><a href="#pushing-changes-to-a-public-repository">Pushing changes to a public repository</a></span></dt><dt><span class="section"><a href="#forcing-push">What to do when a push fails</a></span></dt><dt><span class="section"><a href="#setting-up-a-shared-repository">Setting up a shared repository</a></span></dt><dt><span class="section"><a href="#setting-up-gitweb">Allowing web browsing of a repository</a></span></dt></dl></div><p>Another way to submit changes to a project is to tell the maintainer
|
||
of that project to pull the changes from your repository using
|
||
git-pull(1). In the section "<a class="link" href="#getting-updates-With-git-pull" title="Chapter 29. Getting updates with git pull">Getting updates with <code class="literal">git pull</code></a>" we described this as a way to get
|
||
updates from the "main" repository, but it works just as well in the
|
||
other direction.</p><p>If you and the maintainer both have accounts on the same machine, then
|
||
you can just pull changes from each other’s repositories directly;
|
||
commands that accept repository URLs as arguments will also accept a
|
||
local directory name:</p><pre class="screen">$ git clone /path/to/repository
|
||
$ git pull /path/to/other/repository</pre><p>or an ssh URL:</p><pre class="screen">$ git clone ssh://yourhost/~you/repository</pre><p>For projects with few developers, or for synchronizing a few private
|
||
repositories, this may be all you need.</p><p>However, the more common way to do this is to maintain a separate public
|
||
repository (usually on a different host) for others to pull changes
|
||
from. This is usually more convenient, and allows you to cleanly
|
||
separate private work in progress from publicly visible work.</p><p>You will continue to do your day-to-day work in your personal
|
||
repository, but periodically "push" changes from your personal
|
||
repository into your public repository, allowing other developers to
|
||
pull from that repository. So the flow of changes, in a situation
|
||
where there is one other developer with a public repository, looks
|
||
like this:</p><pre class="literallayout"> you push
|
||
your personal repo ------------------> your public repo
|
||
^ |
|
||
| |
|
||
| you pull | they pull
|
||
| |
|
||
| |
|
||
| they push V
|
||
their public repo <------------------- their repo</pre><p>We explain how to do this in the following sections.</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="setting-up-a-public-repository"></a>Setting up a public repository</h2></div></div></div><p>Assume your personal repository is in the directory <code class="literal">~/proj</code>. We
|
||
first create a new clone of the repository and tell <code class="literal">git daemon</code> that it
|
||
is meant to be public:</p><pre class="screen">$ git clone --bare ~/proj proj.git
|
||
$ touch proj.git/git-daemon-export-ok</pre><p>The resulting directory proj.git contains a "bare" git repository—it is
|
||
just the contents of the <code class="literal">.git</code> directory, without any files checked out
|
||
around it.</p><p>Next, copy <code class="literal">proj.git</code> to the server where you plan to host the
|
||
public repository. You can use scp, rsync, or whatever is most
|
||
convenient.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="exporting-via-git"></a>Exporting a Git repository via the Git protocol</h2></div></div></div><p>This is the preferred method.</p><p>If someone else administers the server, they should tell you what
|
||
directory to put the repository in, and what <code class="literal">git://</code> URL it will
|
||
appear at. You can then skip to the section
|
||
"<a class="link" href="#pushing-changes-to-a-public-repository" title="Pushing changes to a public repository">Pushing changes to a public
|
||
repository</a>", below.</p><p>Otherwise, all you need to do is start git-daemon(1); it will
|
||
listen on port 9418. By default, it will allow access to any directory
|
||
that looks like a Git directory and contains the magic file
|
||
git-daemon-export-ok. Passing some directory paths as <code class="literal">git daemon</code>
|
||
arguments will further restrict the exports to those paths.</p><p>You can also run <code class="literal">git daemon</code> as an inetd service; see the
|
||
git-daemon(1) man page for details. (See especially the
|
||
examples section.)</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="exporting-via-http"></a>Exporting a git repository via HTTP</h2></div></div></div><p>The Git protocol gives better performance and reliability, but on a
|
||
host with a web server set up, HTTP exports may be simpler to set up.</p><p>All you need to do is place the newly created bare Git repository in
|
||
a directory that is exported by the web server, and make some
|
||
adjustments to give web clients some extra information they need:</p><pre class="screen">$ mv proj.git /home/you/public_html/proj.git
|
||
$ cd proj.git
|
||
$ git --bare update-server-info
|
||
$ mv hooks/post-update.sample hooks/post-update</pre><p>(For an explanation of the last two lines, see
|
||
git-update-server-info(1) and githooks(5).)</p><p>Advertise the URL of <code class="literal">proj.git</code>. Anybody else should then be able to
|
||
clone or pull from that URL, for example with a command line like:</p><pre class="screen">$ git clone http://yourserver.com/~you/proj.git</pre><p>(See also
|
||
<a class="ulink" href="howto/setup-git-server-over-http.html" target="_top">setup-git-server-over-http</a>
|
||
for a slightly more sophisticated setup using WebDAV which also
|
||
allows pushing over HTTP.)</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="pushing-changes-to-a-public-repository"></a>Pushing changes to a public repository</h2></div></div></div><p>Note that the two techniques outlined above (exporting via
|
||
<a class="link" href="#exporting-via-http" title="Exporting a git repository via HTTP">http</a> or <a class="link" href="#exporting-via-git" title="Exporting a Git repository via the Git protocol">git</a>) allow other
|
||
maintainers to fetch your latest changes, but they do not allow write
|
||
access, which you will need to update the public repository with the
|
||
latest changes created in your private repository.</p><p>The simplest way to do this is using git-push(1) and ssh; to
|
||
update the remote branch named <code class="literal">master</code> with the latest state of your
|
||
branch named <code class="literal">master</code>, run</p><pre class="screen">$ git push ssh://yourserver.com/~you/proj.git master:master</pre><p>or just</p><pre class="screen">$ git push ssh://yourserver.com/~you/proj.git master</pre><p>As with <code class="literal">git fetch</code>, <code class="literal">git push</code> will complain if this does not result in a
|
||
<a class="link" href="#fast-forwards" title="Chapter 25. Fast-forward merges">fast-forward</a>; see the following section for details on
|
||
handling this case.</p><p>Note that the target of a <code class="literal">push</code> is normally a
|
||
<a class="link" href="#def_bare_repository">bare</a> repository. You can also push to a
|
||
repository that has a checked-out working tree, but a push to update the
|
||
currently checked-out branch is denied by default to prevent confusion.
|
||
See the description of the receive.denyCurrentBranch option
|
||
in git-config(1) for details.</p><p>As with <code class="literal">git fetch</code>, you may also set up configuration options to
|
||
save typing; so, for example:</p><pre class="screen">$ git remote add public-repo ssh://yourserver.com/~you/proj.git</pre><p>adds the following to <code class="literal">.git/config</code>:</p><pre class="screen">[remote "public-repo"]
|
||
url = yourserver.com:proj.git
|
||
fetch = +refs/heads/*:refs/remotes/example/*</pre><p>which lets you do the same push with just</p><pre class="screen">$ git push public-repo master</pre><p>See the explanations of the <code class="literal">remote.<name>.url</code>,
|
||
<code class="literal">branch.<name>.remote</code>, and <code class="literal">remote.<name>.push</code> options in
|
||
git-config(1) for details.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="forcing-push"></a>What to do when a push fails</h2></div></div></div><p>If a push would not result in a <a class="link" href="#fast-forwards" title="Chapter 25. Fast-forward merges">fast-forward</a> of the
|
||
remote branch, then it will fail with an error like:</p><pre class="screen"> ! [rejected] master -> master (non-fast-forward)
|
||
error: failed to push some refs to '...'
|
||
hint: Updates were rejected because the tip of your current branch is behind
|
||
hint: its remote counterpart. Integrate the remote changes (e.g.
|
||
hint: 'git pull ...') before pushing again.
|
||
hint: See the 'Note about fast-forwards' in 'git push --help' for details.</pre><p>This can happen, for example, if you:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">use <code class="literal">git reset --hard</code> to remove already-published commits, or</li><li class="listitem">use <code class="literal">git commit --amend</code> to replace already-published commits
|
||
(as in <a class="xref" href="#fixing-a-mistake-by-rewriting-history" title="Fixing a mistake by rewriting history">the section called “Fixing a mistake by rewriting history”</a>), or</li><li class="listitem">use <code class="literal">git rebase</code> to rebase any already-published commits (as
|
||
in <a class="xref" href="#using-git-rebase" title="Chapter 36. Keeping a patch series up to date using git rebase">Chapter 36, <i>Keeping a patch series up to date using git rebase</i></a>).</li></ul></div><p>You may force <code class="literal">git push</code> to perform the update anyway by preceding the
|
||
branch name with a plus sign:</p><pre class="screen">$ git push ssh://yourserver.com/~you/proj.git +master</pre><p>Note the addition of the <code class="literal">+</code> sign. Alternatively, you can use the
|
||
<code class="literal">-f</code> flag to force the remote update, as in:</p><pre class="screen">$ git push -f ssh://yourserver.com/~you/proj.git master</pre><p>Normally whenever a branch head in a public repository is modified, it
|
||
is modified to point to a descendant of the commit that it pointed to
|
||
before. By forcing a push in this situation, you break that convention.
|
||
(See <a class="xref" href="#problems-With-rewriting-history" title="Chapter 41. Problems with rewriting history">Chapter 41, <i>Problems with rewriting history</i></a>.)</p><p>Nevertheless, this is a common practice for people that need a simple
|
||
way to publish a work-in-progress patch series, and it is an acceptable
|
||
compromise as long as you warn other developers that this is how you
|
||
intend to manage the branch.</p><p>It’s also possible for a push to fail in this way when other people have
|
||
the right to push to the same repository. In that case, the correct
|
||
solution is to retry the push after first updating your work: either by a
|
||
pull, or by a fetch followed by a rebase; see the
|
||
<a class="link" href="#setting-up-a-shared-repository" title="Setting up a shared repository">next section</a> and
|
||
gitcvs-migration(7) for more.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="setting-up-a-shared-repository"></a>Setting up a shared repository</h2></div></div></div><p>Another way to collaborate is by using a model similar to that
|
||
commonly used in CVS, where several developers with special rights
|
||
all push to and pull from a single shared repository. See
|
||
gitcvs-migration(7) for instructions on how to
|
||
set this up.</p><p>However, while there is nothing wrong with Git’s support for shared
|
||
repositories, this mode of operation is not generally recommended,
|
||
simply because the mode of collaboration that Git supports—by
|
||
exchanging patches and pulling from public repositories—has so many
|
||
advantages over the central shared repository:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">Git’s ability to quickly import and merge patches allows a
|
||
single maintainer to process incoming changes even at very
|
||
high rates. And when that becomes too much, <code class="literal">git pull</code> provides
|
||
an easy way for that maintainer to delegate this job to other
|
||
maintainers while still allowing optional review of incoming
|
||
changes.</li><li class="listitem">Since every developer’s repository has the same complete copy
|
||
of the project history, no repository is special, and it is
|
||
trivial for another developer to take over maintenance of a
|
||
project, either by mutual agreement, or because a maintainer
|
||
becomes unresponsive or difficult to work with.</li><li class="listitem">The lack of a central group of "committers" means there is
|
||
less need for formal decisions about who is "in" and who is
|
||
"out".</li></ul></div></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="setting-up-gitweb"></a>Allowing web browsing of a repository</h2></div></div></div><p>The gitweb cgi script provides users an easy way to browse your
|
||
project’s revisions, file contents and logs without having to install
|
||
Git. Features like RSS/Atom feeds and blame/annotation details may
|
||
optionally be enabled.</p><p>The git-instaweb(1) command provides a simple way to start
|
||
browsing the repository using gitweb. The default server when using
|
||
instaweb is lighttpd.</p><p>See the file gitweb/INSTALL in the Git source tree and
|
||
gitweb(1) for instructions on details setting up a permanent
|
||
installation with a CGI or Perl capable server.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="how-to-get-a-git-repository-with-minimal-history"></a>Chapter 33. How to get a Git repository with minimal history</h2></div></div></div><p>A <a class="link" href="#def_shallow_clone">shallow clone</a>, with its truncated
|
||
history, is useful when one is interested only in recent history
|
||
of a project and getting full history from the upstream is
|
||
expensive.</p><p>A <a class="link" href="#def_shallow_clone">shallow clone</a> is created by specifying
|
||
the git-clone(1) <code class="literal">--depth</code> switch. The depth can later be
|
||
changed with the git-fetch(1) <code class="literal">--depth</code> switch, or full
|
||
history restored with <code class="literal">--unshallow</code>.</p><p>Merging inside a <a class="link" href="#def_shallow_clone">shallow clone</a> will work as long
|
||
as a merge base is in the recent history.
|
||
Otherwise, it will be like merging unrelated histories and may
|
||
have to result in huge conflicts. This limitation may make such
|
||
a repository unsuitable to be used in merge based workflows.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="sharing-development-examples"></a>Chapter 34. Examples</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#maintaining-topic-branches">Maintaining topic branches for a Linux subsystem maintainer</a></span></dt></dl></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="maintaining-topic-branches"></a>Maintaining topic branches for a Linux subsystem maintainer</h2></div></div></div><p>This describes how Tony Luck uses Git in his role as maintainer of the
|
||
IA64 architecture for the Linux kernel.</p><p>He uses two public branches:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">A "test" tree into which patches are initially placed so that they
|
||
can get some exposure when integrated with other ongoing development.
|
||
This tree is available to Andrew for pulling into -mm whenever he
|
||
wants.</li><li class="listitem">A "release" tree into which tested patches are moved for final sanity
|
||
checking, and as a vehicle to send them upstream to Linus (by sending
|
||
him a "please pull" request.)</li></ul></div><p>He also uses a set of temporary branches ("topic branches"), each
|
||
containing a logical grouping of patches.</p><p>To set this up, first create your work tree by cloning Linus’s public
|
||
tree:</p><pre class="screen">$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git work
|
||
$ cd work</pre><p>Linus’s tree will be stored in the remote-tracking branch named origin/master,
|
||
and can be updated using git-fetch(1); you can track other
|
||
public trees using git-remote(1) to set up a "remote" and
|
||
git-fetch(1) to keep them up to date; see
|
||
<a class="xref" href="#repositories-and-branches" title="Part I. Repositories and Branches">Part I, “Repositories and Branches”</a>.</p><p>Now create the branches in which you are going to work; these start out
|
||
at the current tip of origin/master branch, and should be set up (using
|
||
the <code class="literal">--track</code> option to git-branch(1)) to merge changes in from
|
||
Linus by default.</p><pre class="screen">$ git branch --track test origin/master
|
||
$ git branch --track release origin/master</pre><p>These can be easily kept up to date using git-pull(1).</p><pre class="screen">$ git checkout test && git pull
|
||
$ git checkout release && git pull</pre><p>Important note! If you have any local changes in these branches, then
|
||
this merge will create a commit object in the history (with no local
|
||
changes Git will simply do a "fast-forward" merge). Many people dislike
|
||
the "noise" that this creates in the Linux history, so you should avoid
|
||
doing this capriciously in the <code class="literal">release</code> branch, as these noisy commits
|
||
will become part of the permanent history when you ask Linus to pull
|
||
from the release branch.</p><p>A few configuration variables (see git-config(1)) can
|
||
make it easy to push both branches to your public tree. (See
|
||
<a class="xref" href="#setting-up-a-public-repository" title="Setting up a public repository">the section called “Setting up a public repository”</a>.)</p><pre class="screen">$ cat >> .git/config <<EOF
|
||
[remote "mytree"]
|
||
url = master.kernel.org:/pub/scm/linux/kernel/git/aegl/linux.git
|
||
push = release
|
||
push = test
|
||
EOF</pre><p>Then you can push both the test and release trees using
|
||
git-push(1):</p><pre class="screen">$ git push mytree</pre><p>or push just one of the test and release branches using:</p><pre class="screen">$ git push mytree test</pre><p>or</p><pre class="screen">$ git push mytree release</pre><p>Now to apply some patches from the community. Think of a short
|
||
snappy name for a branch to hold this patch (or related group of
|
||
patches), and create a new branch from a recent stable tag of
|
||
Linus’s branch. Picking a stable base for your branch will:
|
||
1) help you: by avoiding inclusion of unrelated and perhaps lightly
|
||
tested changes
|
||
2) help future bug hunters that use <code class="literal">git bisect</code> to find problems</p><pre class="screen">$ git checkout -b speed-up-spinlocks v2.6.35</pre><p>Now you apply the patch(es), run some tests, and commit the change(s). If
|
||
the patch is a multi-part series, then you should apply each as a separate
|
||
commit to this branch.</p><pre class="screen">$ ... patch ... test ... commit [ ... patch ... test ... commit ]*</pre><p>When you are happy with the state of this change, you can merge it into the
|
||
"test" branch in preparation to make it public:</p><pre class="screen">$ git checkout test && git merge speed-up-spinlocks</pre><p>It is unlikely that you would have any conflicts here … but you might if you
|
||
spent a while on this step and had also pulled new versions from upstream.</p><p>Sometime later when enough time has passed and testing done, you can pull the
|
||
same branch into the <code class="literal">release</code> tree ready to go upstream. This is where you
|
||
see the value of keeping each patch (or patch series) in its own branch. It
|
||
means that the patches can be moved into the <code class="literal">release</code> tree in any order.</p><pre class="screen">$ git checkout release && git merge speed-up-spinlocks</pre><p>After a while, you will have a number of branches, and despite the
|
||
well chosen names you picked for each of them, you may forget what
|
||
they are for, or what status they are in. To get a reminder of what
|
||
changes are in a specific branch, use:</p><pre class="screen">$ git log linux..branchname | git shortlog</pre><p>To see whether it has already been merged into the test or release branches,
|
||
use:</p><pre class="screen">$ git log test..branchname</pre><p>or</p><pre class="screen">$ git log release..branchname</pre><p>(If this branch has not yet been merged, you will see some log entries.
|
||
If it has been merged, then there will be no output.)</p><p>Once a patch completes the great cycle (moving from test to release,
|
||
then pulled by Linus, and finally coming back into your local
|
||
<code class="literal">origin/master</code> branch), the branch for this change is no longer needed.
|
||
You detect this when the output from:</p><pre class="screen">$ git log origin..branchname</pre><p>is empty. At this point the branch can be deleted:</p><pre class="screen">$ git branch -d branchname</pre><p>Some changes are so trivial that it is not necessary to create a separate
|
||
branch and then merge into each of the test and release branches. For
|
||
these changes, just apply directly to the <code class="literal">release</code> branch, and then
|
||
merge that into the <code class="literal">test</code> branch.</p><p>After pushing your work to <code class="literal">mytree</code>, you can use
|
||
git-request-pull(1) to prepare a "please pull" request message
|
||
to send to Linus:</p><pre class="screen">$ git push mytree
|
||
$ git request-pull origin mytree release</pre><p>Here are some of the scripts that simplify all this even further.</p><pre class="screen">==== update script ====
|
||
# Update a branch in my Git tree. If the branch to be updated
|
||
# is origin, then pull from kernel.org. Otherwise merge
|
||
# origin/master branch into test|release branch
|
||
|
||
case "$1" in
|
||
test|release)
|
||
git checkout $1 && git pull . origin
|
||
;;
|
||
origin)
|
||
before=$(git rev-parse refs/remotes/origin/master)
|
||
git fetch origin
|
||
after=$(git rev-parse refs/remotes/origin/master)
|
||
if [ $before != $after ]
|
||
then
|
||
git log $before..$after | git shortlog
|
||
fi
|
||
;;
|
||
*)
|
||
echo "usage: $0 origin|test|release" 1>&2
|
||
exit 1
|
||
;;
|
||
esac</pre><pre class="screen">==== merge script ====
|
||
# Merge a branch into either the test or release branch
|
||
|
||
pname=$0
|
||
|
||
usage()
|
||
{
|
||
echo "usage: $pname branch test|release" 1>&2
|
||
exit 1
|
||
}
|
||
|
||
git show-ref -q --verify -- refs/heads/"$1" || {
|
||
echo "Can't see branch <$1>" 1>&2
|
||
usage
|
||
}
|
||
|
||
case "$2" in
|
||
test|release)
|
||
if [ $(git log $2..$1 | wc -c) -eq 0 ]
|
||
then
|
||
echo $1 already merged into $2 1>&2
|
||
exit 1
|
||
fi
|
||
git checkout $2 && git pull . $1
|
||
;;
|
||
*)
|
||
usage
|
||
;;
|
||
esac</pre><pre class="screen">==== status script ====
|
||
# report on status of my ia64 Git tree
|
||
|
||
gb=$(tput setab 2)
|
||
rb=$(tput setab 1)
|
||
restore=$(tput setab 9)
|
||
|
||
if [ `git rev-list test..release | wc -c` -gt 0 ]
|
||
then
|
||
echo $rb Warning: commits in release that are not in test $restore
|
||
git log test..release
|
||
fi
|
||
|
||
for branch in `git show-ref --heads | sed 's|^.*/||'`
|
||
do
|
||
if [ $branch = test -o $branch = release ]
|
||
then
|
||
continue
|
||
fi
|
||
|
||
echo -n $gb ======= $branch ====== $restore " "
|
||
status=
|
||
for ref in test release origin/master
|
||
do
|
||
if [ `git rev-list $ref..$branch | wc -c` -gt 0 ]
|
||
then
|
||
status=$status${ref:0:1}
|
||
fi
|
||
done
|
||
case $status in
|
||
trl)
|
||
echo $rb Need to pull into test $restore
|
||
;;
|
||
rl)
|
||
echo "In test"
|
||
;;
|
||
l)
|
||
echo "Waiting for linus"
|
||
;;
|
||
"")
|
||
echo $rb All done $restore
|
||
;;
|
||
*)
|
||
echo $rb "<$status>" $restore
|
||
;;
|
||
esac
|
||
git log origin/master..$branch | git shortlog
|
||
done</pre></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="cleaning-up-history"></a>Part V. Rewriting history and maintaining patch series</h1></div></div></div><div class="partintro"><div></div><p>Normally commits are only added to a project, never taken away or
|
||
replaced. Git is designed with this assumption, and violating it will
|
||
cause Git’s merge machinery (for example) to do the wrong thing.</p><p>However, there is a situation in which it can be useful to violate this
|
||
assumption.</p><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#patch-series">35. Creating the perfect patch series</a></span></dt><dt><span class="chapter"><a href="#using-git-rebase">36. Keeping a patch series up to date using git rebase</a></span></dt><dt><span class="chapter"><a href="#rewriting-one-commit">37. Rewriting a single commit</a></span></dt><dt><span class="chapter"><a href="#reordering-patch-series">38. Reordering or selecting from a patch series</a></span></dt><dt><span class="chapter"><a href="#interactive-rebase">39. Using interactive rebases</a></span></dt><dt><span class="chapter"><a href="#patch-series-tools">40. Other tools</a></span></dt><dt><span class="chapter"><a href="#problems-With-rewriting-history">41. Problems with rewriting history</a></span></dt><dt><span class="chapter"><a href="#bisect-merges">42. Why bisecting merge commits can be harder than bisecting linear history</a></span></dt></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="patch-series"></a>Chapter 35. Creating the perfect patch series</h2></div></div></div><p>Suppose you are a contributor to a large project, and you want to add a
|
||
complicated feature, and to present it to the other developers in a way
|
||
that makes it easy for them to read your changes, verify that they are
|
||
correct, and understand why you made each change.</p><p>If you present all of your changes as a single patch (or commit), they
|
||
may find that it is too much to digest all at once.</p><p>If you present them with the entire history of your work, complete with
|
||
mistakes, corrections, and dead ends, they may be overwhelmed.</p><p>So the ideal is usually to produce a series of patches such that:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">Each patch can be applied in order.</li><li class="listitem">Each patch includes a single logical change, together with a
|
||
message explaining the change.</li><li class="listitem">No patch introduces a regression: after applying any initial
|
||
part of the series, the resulting project still compiles and
|
||
works, and has no bugs that it didn’t have before.</li><li class="listitem">The complete series produces the same end result as your own
|
||
(probably much messier!) development process did.</li></ol></div><p>We will introduce some tools that can help you do this, explain how to
|
||
use them, and then explain some of the problems that can arise because
|
||
you are rewriting history.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="using-git-rebase"></a>Chapter 36. Keeping a patch series up to date using git rebase</h2></div></div></div><p>Suppose that you create a branch <code class="literal">mywork</code> on a remote-tracking branch
|
||
<code class="literal">origin</code>, and create some commits on top of it:</p><pre class="screen">$ git checkout -b mywork origin
|
||
$ vi file.txt
|
||
$ git commit
|
||
$ vi otherfile.txt
|
||
$ git commit
|
||
...</pre><p>You have performed no merges into mywork, so it is just a simple linear
|
||
sequence of patches on top of <code class="literal">origin</code>:</p><pre class="literallayout"> o--o--O <-- origin
|
||
\
|
||
a--b--c <-- mywork</pre><p>Some more interesting work has been done in the upstream project, and
|
||
<code class="literal">origin</code> has advanced:</p><pre class="literallayout"> o--o--O--o--o--o <-- origin
|
||
\
|
||
a--b--c <-- mywork</pre><p>At this point, you could use <code class="literal">pull</code> to merge your changes back in;
|
||
the result would create a new merge commit, like this:</p><pre class="literallayout"> o--o--O--o--o--o <-- origin
|
||
\ \
|
||
a--b--c--m <-- mywork</pre><p>However, if you prefer to keep the history in mywork a simple series of
|
||
commits without any merges, you may instead choose to use
|
||
git-rebase(1):</p><pre class="screen">$ git checkout mywork
|
||
$ git rebase origin</pre><p>This will remove each of your commits from mywork, temporarily saving
|
||
them as patches (in a directory named <code class="literal">.git/rebase-apply</code>), update mywork to
|
||
point at the latest version of origin, then apply each of the saved
|
||
patches to the new mywork. The result will look like:</p><pre class="literallayout"> o--o--O--o--o--o <-- origin
|
||
\
|
||
a'--b'--c' <-- mywork</pre><p>In the process, it may discover conflicts. In that case it will stop
|
||
and allow you to fix the conflicts; after fixing conflicts, use <code class="literal">git add</code>
|
||
to update the index with those contents, and then, instead of
|
||
running <code class="literal">git commit</code>, just run</p><pre class="screen">$ git rebase --continue</pre><p>and Git will continue applying the rest of the patches.</p><p>At any point you may use the <code class="literal">--abort</code> option to abort this process and
|
||
return mywork to the state it had before you started the rebase:</p><pre class="screen">$ git rebase --abort</pre><p>If you need to reorder or edit a number of commits in a branch, it may
|
||
be easier to use <code class="literal">git rebase -i</code>, which allows you to reorder and
|
||
squash commits, as well as marking them for individual editing during
|
||
the rebase. See <a class="xref" href="#interactive-rebase" title="Chapter 39. Using interactive rebases">Chapter 39, <i>Using interactive rebases</i></a> for details, and
|
||
<a class="xref" href="#reordering-patch-series" title="Chapter 38. Reordering or selecting from a patch series">Chapter 38, <i>Reordering or selecting from a patch series</i></a> for alternatives.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="rewriting-one-commit"></a>Chapter 37. Rewriting a single commit</h2></div></div></div><p>We saw in <a class="xref" href="#fixing-a-mistake-by-rewriting-history" title="Fixing a mistake by rewriting history">the section called “Fixing a mistake by rewriting history”</a> that you can replace the
|
||
most recent commit using</p><pre class="screen">$ git commit --amend</pre><p>which will replace the old commit by a new commit incorporating your
|
||
changes, giving you a chance to edit the old commit message first.
|
||
This is useful for fixing typos in your last commit, or for adjusting
|
||
the patch contents of a poorly staged commit.</p><p>If you need to amend commits from deeper in your history, you can
|
||
use <a class="link" href="#interactive-rebase" title="Chapter 39. Using interactive rebases">interactive rebase’s <code class="literal">edit</code> instruction</a>.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="reordering-patch-series"></a>Chapter 38. Reordering or selecting from a patch series</h2></div></div></div><p>Sometimes you want to edit a commit deeper in your history. One
|
||
approach is to use <code class="literal">git format-patch</code> to create a series of patches
|
||
and then reset the state to before the patches:</p><pre class="screen">$ git format-patch origin
|
||
$ git reset --hard origin</pre><p>Then modify, reorder, or eliminate patches as needed before applying
|
||
them again with git-am(1):</p><pre class="screen">$ git am *.patch</pre></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="interactive-rebase"></a>Chapter 39. Using interactive rebases</h2></div></div></div><p>You can also edit a patch series with an interactive rebase. This is
|
||
the same as <a class="link" href="#reordering-patch-series" title="Chapter 38. Reordering or selecting from a patch series">reordering a patch series using
|
||
<code class="literal">format-patch</code></a>, so use whichever interface you like best.</p><p>Rebase your current HEAD on the last commit you want to retain as-is.
|
||
For example, if you want to reorder the last 5 commits, use:</p><pre class="screen">$ git rebase -i HEAD~5</pre><p>This will open your editor with a list of steps to be taken to perform
|
||
your rebase.</p><pre class="screen">pick deadbee The oneline of this commit
|
||
pick fa1afe1 The oneline of the next commit
|
||
...
|
||
|
||
# Rebase c0ffeee..deadbee onto c0ffeee
|
||
#
|
||
# Commands:
|
||
# p, pick = use commit
|
||
# r, reword = use commit, but edit the commit message
|
||
# e, edit = use commit, but stop for amending
|
||
# s, squash = use commit, but meld into previous commit
|
||
# f, fixup = like "squash", but discard this commit's log message
|
||
# x, exec = run command (the rest of the line) using shell
|
||
#
|
||
# These lines can be re-ordered; they are executed from top to bottom.
|
||
#
|
||
# If you remove a line here THAT COMMIT WILL BE LOST.
|
||
#
|
||
# However, if you remove everything, the rebase will be aborted.
|
||
#
|
||
# Note that empty commits are commented out</pre><p>As explained in the comments, you can reorder commits, squash them
|
||
together, edit commit messages, etc. by editing the list. Once you
|
||
are satisfied, save the list and close your editor, and the rebase
|
||
will begin.</p><p>The rebase will stop where <code class="literal">pick</code> has been replaced with <code class="literal">edit</code> or
|
||
when a step in the list fails to mechanically resolve conflicts and
|
||
needs your help. When you are done editing and/or resolving conflicts
|
||
you can continue with <code class="literal">git rebase --continue</code>. If you decide that
|
||
things are getting too hairy, you can always bail out with <code class="literal">git rebase
|
||
--abort</code>. Even after the rebase is complete, you can still recover
|
||
the original branch by using the <a class="link" href="#reflogs" title="Reflogs">reflog</a>.</p><p>For a more detailed discussion of the procedure and additional tips,
|
||
see the "INTERACTIVE MODE" section of git-rebase(1).</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="patch-series-tools"></a>Chapter 40. Other tools</h2></div></div></div><p>There are numerous other tools, such as StGit, which exist for the
|
||
purpose of maintaining a patch series. These are outside of the scope of
|
||
this manual.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="problems-With-rewriting-history"></a>Chapter 41. Problems with rewriting history</h2></div></div></div><p>The primary problem with rewriting the history of a branch has to do
|
||
with merging. Suppose somebody fetches your branch and merges it into
|
||
their branch, with a result something like this:</p><pre class="literallayout"> o--o--O--o--o--o <-- origin
|
||
\ \
|
||
t--t--t--m <-- their branch:</pre><p>Then suppose you modify the last three commits:</p><pre class="literallayout"> o--o--o <-- new head of origin
|
||
/
|
||
o--o--O--o--o--o <-- old head of origin</pre><p>If we examined all this history together in one repository, it will
|
||
look like:</p><pre class="literallayout"> o--o--o <-- new head of origin
|
||
/
|
||
o--o--O--o--o--o <-- old head of origin
|
||
\ \
|
||
t--t--t--m <-- their branch:</pre><p>Git has no way of knowing that the new head is an updated version of
|
||
the old head; it treats this situation exactly the same as it would if
|
||
two developers had independently done the work on the old and new heads
|
||
in parallel. At this point, if someone attempts to merge the new head
|
||
in to their branch, Git will attempt to merge together the two (old and
|
||
new) lines of development, instead of trying to replace the old by the
|
||
new. The results are likely to be unexpected.</p><p>You may still choose to publish branches whose history is rewritten,
|
||
and it may be useful for others to be able to fetch those branches in
|
||
order to examine or test them, but they should not attempt to pull such
|
||
branches into their own work.</p><p>For true distributed development that supports proper merging,
|
||
published branches should never be rewritten.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="bisect-merges"></a>Chapter 42. Why bisecting merge commits can be harder than bisecting linear history</h2></div></div></div><p>The git-bisect(1) command correctly handles history that
|
||
includes merge commits. However, when the commit that it finds is a
|
||
merge commit, the user may need to work harder than usual to figure out
|
||
why that commit introduced a problem.</p><p>Imagine this history:</p><pre class="literallayout"> ---Z---o---X---...---o---A---C---D
|
||
\ /
|
||
o---o---Y---...---o---B</pre><p>Suppose that on the upper line of development, the meaning of one
|
||
of the functions that exists at Z is changed at commit X. The
|
||
commits from Z leading to A change both the function’s
|
||
implementation and all calling sites that exist at Z, as well
|
||
as new calling sites they add, to be consistent. There is no
|
||
bug at A.</p><p>Suppose that in the meantime on the lower line of development somebody
|
||
adds a new calling site for that function at commit Y. The
|
||
commits from Z leading to B all assume the old semantics of that
|
||
function and the callers and the callee are consistent with each
|
||
other. There is no bug at B, either.</p><p>Suppose further that the two development lines merge cleanly at C,
|
||
so no conflict resolution is required.</p><p>Nevertheless, the code at C is broken, because the callers added
|
||
on the lower line of development have not been converted to the new
|
||
semantics introduced on the upper line of development. So if all
|
||
you know is that D is bad, that Z is good, and that
|
||
git-bisect(1) identifies C as the culprit, how will you
|
||
figure out that the problem is due to this change in semantics?</p><p>When the result of a <code class="literal">git bisect</code> is a non-merge commit, you should
|
||
normally be able to discover the problem by examining just that commit.
|
||
Developers can make this easy by breaking their changes into small
|
||
self-contained commits. That won’t help in the case above, however,
|
||
because the problem isn’t obvious from examination of any single
|
||
commit; instead, a global view of the development is required. To
|
||
make matters worse, the change in semantics in the problematic
|
||
function may be just one small part of the changes in the upper
|
||
line of development.</p><p>On the other hand, if instead of merging at C you had rebased the
|
||
history between Z to B on top of A, you would have gotten this
|
||
linear history:</p><pre class="literallayout"> ---Z---o---X--...---o---A---o---o---Y*--...---o---B*--D*</pre><p>Bisecting between Z and D* would hit a single culprit commit Y*,
|
||
and understanding why Y* was broken would probably be easier.</p><p>Partly for this reason, many experienced Git users, even when
|
||
working on an otherwise merge-heavy project, keep the history
|
||
linear by rebasing against the latest upstream version before
|
||
publishing.</p></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="advanced-branch-management"></a>Part VI. Advanced branch management</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#fetching-individual-branches">43. Fetching individual branches</a></span></dt><dt><span class="chapter"><a href="#fetch-fast-forwards">44. git fetch and fast-forwards</a></span></dt><dt><span class="chapter"><a href="#forcing-fetch">45. Forcing git fetch to do non-fast-forward updates</a></span></dt><dt><span class="chapter"><a href="#remote-branch-configuration">46. Configuring remote-tracking branches</a></span></dt></dl></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="fetching-individual-branches"></a>Chapter 43. Fetching individual branches</h2></div></div></div><p>Instead of using git-remote(1), you can also choose just
|
||
to update one branch at a time, and to store it locally under an
|
||
arbitrary name:</p><pre class="screen">$ git fetch origin todo:my-todo-work</pre><p>The first argument, <code class="literal">origin</code>, just tells Git to fetch from the
|
||
repository you originally cloned from. The second argument tells Git
|
||
to fetch the branch named <code class="literal">todo</code> from the remote repository, and to
|
||
store it locally under the name <code class="literal">refs/heads/my-todo-work</code>.</p><p>You can also fetch branches from other repositories; so</p><pre class="screen">$ git fetch git://example.com/proj.git master:example-master</pre><p>will create a new branch named <code class="literal">example-master</code> and store in it the
|
||
branch named <code class="literal">master</code> from the repository at the given URL. If you
|
||
already have a branch named example-master, it will attempt to
|
||
<a class="link" href="#fast-forwards" title="Chapter 25. Fast-forward merges">fast-forward</a> to the commit given by example.com’s
|
||
master branch. In more detail:</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="fetch-fast-forwards"></a>Chapter 44. git fetch and fast-forwards</h2></div></div></div><p>In the previous example, when updating an existing branch, <code class="literal">git fetch</code>
|
||
checks to make sure that the most recent commit on the remote
|
||
branch is a descendant of the most recent commit on your copy of the
|
||
branch before updating your copy of the branch to point at the new
|
||
commit. Git calls this process a <a class="link" href="#fast-forwards" title="Chapter 25. Fast-forward merges">fast-forward</a>.</p><p>A fast-forward looks something like this:</p><pre class="literallayout"> o--o--o--o <-- old head of the branch
|
||
\
|
||
o--o--o <-- new head of the branch</pre><p>In some cases it is possible that the new head will <span class="strong"><strong>not</strong></span> actually be
|
||
a descendant of the old head. For example, the developer may have
|
||
realized she made a serious mistake, and decided to backtrack,
|
||
resulting in a situation like:</p><pre class="literallayout"> o--o--o--o--a--b <-- old head of the branch
|
||
\
|
||
o--o--o <-- new head of the branch</pre><p>In this case, <code class="literal">git fetch</code> will fail, and print out a warning.</p><p>In that case, you can still force Git to update to the new head, as
|
||
described in the following section. However, note that in the
|
||
situation above this may mean losing the commits labeled <code class="literal">a</code> and <code class="literal">b</code>,
|
||
unless you’ve already created a reference of your own pointing to
|
||
them.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="forcing-fetch"></a>Chapter 45. Forcing git fetch to do non-fast-forward updates</h2></div></div></div><p>If git fetch fails because the new head of a branch is not a
|
||
descendant of the old head, you may force the update with:</p><pre class="screen">$ git fetch git://example.com/proj.git +master:refs/remotes/example/master</pre><p>Note the addition of the <code class="literal">+</code> sign. Alternatively, you can use the <code class="literal">-f</code>
|
||
flag to force updates of all the fetched branches, as in:</p><pre class="screen">$ git fetch -f origin</pre><p>Be aware that commits that the old version of example/master pointed at
|
||
may be lost, as we saw in the previous section.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="remote-branch-configuration"></a>Chapter 46. Configuring remote-tracking branches</h2></div></div></div><p>We saw above that <code class="literal">origin</code> is just a shortcut to refer to the
|
||
repository that you originally cloned from. This information is
|
||
stored in Git configuration variables, which you can see using
|
||
git-config(1):</p><pre class="screen">$ git config -l
|
||
core.repositoryformatversion=0
|
||
core.filemode=true
|
||
core.logallrefupdates=true
|
||
remote.origin.url=git://git.kernel.org/pub/scm/git/git.git
|
||
remote.origin.fetch=+refs/heads/*:refs/remotes/origin/*
|
||
branch.master.remote=origin
|
||
branch.master.merge=refs/heads/master</pre><p>If there are other repositories that you also use frequently, you can
|
||
create similar configuration options to save typing; for example,</p><pre class="screen">$ git remote add example git://example.com/proj.git</pre><p>adds the following to <code class="literal">.git/config</code>:</p><pre class="screen">[remote "example"]
|
||
url = git://example.com/proj.git
|
||
fetch = +refs/heads/*:refs/remotes/example/*</pre><p>Also note that the above configuration can be performed by directly
|
||
editing the file <code class="literal">.git/config</code> instead of using git-remote(1).</p><p>After configuring the remote, the following three commands will do the
|
||
same thing:</p><pre class="screen">$ git fetch git://example.com/proj.git +refs/heads/*:refs/remotes/example/*
|
||
$ git fetch example +refs/heads/*:refs/remotes/example/*
|
||
$ git fetch example</pre><p>See git-config(1) for more details on the configuration
|
||
options mentioned above and git-fetch(1) for more details on
|
||
the refspec syntax.</p></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="git-concepts"></a>Part VII. Git concepts</h1></div></div></div><div class="partintro"><div></div><p>Git is built on a small number of simple but powerful ideas. While it
|
||
is possible to get things done without understanding them, you will find
|
||
Git much more intuitive if you do.</p><p>We start with the most important, the <a class="link" href="#def_object_database">object
|
||
database</a> and the <a class="link" href="#def_index">index</a>.</p><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#the-object-database">47. The Object Database</a></span></dt><dd><dl><dt><span class="section"><a href="#commit-object">Commit Object</a></span></dt><dt><span class="section"><a href="#tree-object">Tree Object</a></span></dt><dt><span class="section"><a href="#blob-object">Blob Object</a></span></dt><dt><span class="section"><a href="#trust">Trust</a></span></dt><dt><span class="section"><a href="#tag-object">Tag Object</a></span></dt><dt><span class="section"><a href="#pack-files">How Git stores objects efficiently: pack files</a></span></dt><dt><span class="section"><a href="#dangling-objects">Dangling objects</a></span></dt><dt><span class="section"><a href="#recovering-from-repository-corruption">Recovering from repository corruption</a></span></dt></dl></dd><dt><span class="chapter"><a href="#the-index">48. The index</a></span></dt></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="the-object-database"></a>Chapter 47. The Object Database</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#commit-object">Commit Object</a></span></dt><dt><span class="section"><a href="#tree-object">Tree Object</a></span></dt><dt><span class="section"><a href="#blob-object">Blob Object</a></span></dt><dt><span class="section"><a href="#trust">Trust</a></span></dt><dt><span class="section"><a href="#tag-object">Tag Object</a></span></dt><dt><span class="section"><a href="#pack-files">How Git stores objects efficiently: pack files</a></span></dt><dt><span class="section"><a href="#dangling-objects">Dangling objects</a></span></dt><dt><span class="section"><a href="#recovering-from-repository-corruption">Recovering from repository corruption</a></span></dt></dl></div><p>We already saw in <a class="xref" href="#understanding-commits" title="Chapter 3. Understanding History: Commits">Chapter 3, <i>Understanding History: Commits</i></a> that all commits are stored
|
||
under a 40-digit "object name". In fact, all the information needed to
|
||
represent the history of a project is stored in objects with such names.
|
||
In each case the name is calculated by taking the SHA-1 hash of the
|
||
contents of the object. The SHA-1 hash is a cryptographic hash function.
|
||
What that means to us is that it is impossible to find two different
|
||
objects with the same name. This has a number of advantages; among
|
||
others:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">Git can quickly determine whether two objects are identical or not,
|
||
just by comparing names.</li><li class="listitem">Since object names are computed the same way in every repository, the
|
||
same content stored in two repositories will always be stored under
|
||
the same name.</li><li class="listitem">Git can detect errors when it reads an object, by checking that the
|
||
object’s name is still the SHA-1 hash of its contents.</li></ul></div><p>(See <a class="xref" href="#object-details" title="Chapter 55. Object storage format">Chapter 55, <i>Object storage format</i></a> for the details of the object formatting and
|
||
SHA-1 calculation.)</p><p>There are four different types of objects: "blob", "tree", "commit", and
|
||
"tag".</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">A <a class="link" href="#def_blob_object">"blob" object</a> is used to store file data.</li><li class="listitem">A <a class="link" href="#def_tree_object">"tree" object</a> ties one or more
|
||
"blob" objects into a directory structure. In addition, a tree object
|
||
can refer to other tree objects, thus creating a directory hierarchy.</li><li class="listitem">A <a class="link" href="#def_commit_object">"commit" object</a> ties such directory hierarchies
|
||
together into a <a class="link" href="#def_DAG">directed acyclic graph</a> of revisions—each
|
||
commit contains the object name of exactly one tree designating the
|
||
directory hierarchy at the time of the commit. In addition, a commit
|
||
refers to "parent" commit objects that describe the history of how we
|
||
arrived at that directory hierarchy.</li><li class="listitem">A <a class="link" href="#def_tag_object">"tag" object</a> symbolically identifies and can be
|
||
used to sign other objects. It contains the object name and type of
|
||
another object, a symbolic name (of course!) and, optionally, a
|
||
signature.</li></ul></div><p>The object types in some more detail:</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="commit-object"></a>Commit Object</h2></div></div></div><p>The "commit" object links a physical state of a tree with a description
|
||
of how we got there and why. Use the <code class="literal">--pretty=raw</code> option to
|
||
git-show(1) or git-log(1) to examine your favorite
|
||
commit:</p><pre class="screen">$ git show -s --pretty=raw 2be7fcb476
|
||
commit 2be7fcb4764f2dbcee52635b91fedb1b3dcf7ab4
|
||
tree fb3a8bdd0ceddd019615af4d57a53f43d8cee2bf
|
||
parent 257a84d9d02e90447b149af58b271c19405edb6a
|
||
author Dave Watson <dwatson@mimvista.com> 1187576872 -0400
|
||
committer Junio C Hamano <gitster@pobox.com> 1187591163 -0700
|
||
|
||
Fix misspelling of 'suppress' in docs
|
||
|
||
Signed-off-by: Junio C Hamano <gitster@pobox.com></pre><p>As you can see, a commit is defined by:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">a tree: The SHA-1 name of a tree object (as defined below), representing
|
||
the contents of a directory at a certain point in time.</li><li class="listitem">parent(s): The SHA-1 name(s) of some number of commits which represent the
|
||
immediately previous step(s) in the history of the project. The
|
||
example above has one parent; merge commits may have more than
|
||
one. A commit with no parents is called a "root" commit, and
|
||
represents the initial revision of a project. Each project must have
|
||
at least one root. A project can also have multiple roots, though
|
||
that isn’t common (or necessarily a good idea).</li><li class="listitem">an author: The name of the person responsible for this change, together
|
||
with its date.</li><li class="listitem">a committer: The name of the person who actually created the commit,
|
||
with the date it was done. This may be different from the author, for
|
||
example, if the author was someone who wrote a patch and emailed it
|
||
to the person who used it to create the commit.</li><li class="listitem">a comment describing this commit.</li></ul></div><p>Note that a commit does not itself contain any information about what
|
||
actually changed; all changes are calculated by comparing the contents
|
||
of the tree referred to by this commit with the trees associated with
|
||
its parents. In particular, Git does not attempt to record file renames
|
||
explicitly, though it can identify cases where the existence of the same
|
||
file data at changing paths suggests a rename. (See, for example, the
|
||
<code class="literal">-M</code> option to git-diff(1)).</p><p>A commit is usually created by git-commit(1), which creates a
|
||
commit whose parent is normally the current HEAD, and whose tree is
|
||
taken from the content currently stored in the index.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="tree-object"></a>Tree Object</h2></div></div></div><p>The ever-versatile git-show(1) command can also be used to
|
||
examine tree objects, but git-ls-tree(1) will give you more
|
||
details:</p><pre class="screen">$ git ls-tree fb3a8bdd0ce
|
||
100644 blob 63c918c667fa005ff12ad89437f2fdc80926e21c .gitignore
|
||
100644 blob 5529b198e8d14decbe4ad99db3f7fb632de0439d .mailmap
|
||
100644 blob 6ff87c4664981e4397625791c8ea3bbb5f2279a3 COPYING
|
||
040000 tree 2fb783e477100ce076f6bf57e4a6f026013dc745 Documentation
|
||
100755 blob 3c0032cec592a765692234f1cba47dfdcc3a9200 GIT-VERSION-GEN
|
||
100644 blob 289b046a443c0647624607d471289b2c7dcd470b INSTALL
|
||
100644 blob 4eb463797adc693dc168b926b6932ff53f17d0b1 Makefile
|
||
100644 blob 548142c327a6790ff8821d67c2ee1eff7a656b52 README
|
||
...</pre><p>As you can see, a tree object contains a list of entries, each with a
|
||
mode, object type, SHA-1 name, and name, sorted by name. It represents
|
||
the contents of a single directory tree.</p><p>The object type may be a blob, representing the contents of a file, or
|
||
another tree, representing the contents of a subdirectory. Since trees
|
||
and blobs, like all other objects, are named by the SHA-1 hash of their
|
||
contents, two trees have the same SHA-1 name if and only if their
|
||
contents (including, recursively, the contents of all subdirectories)
|
||
are identical. This allows Git to quickly determine the differences
|
||
between two related tree objects, since it can ignore any entries with
|
||
identical object names.</p><p>(Note: in the presence of submodules, trees may also have commits as
|
||
entries. See <a class="xref" href="#submodules" title="Part VIII. Submodules">Part VIII, “Submodules”</a> for documentation.)</p><p>Note that the files all have mode 644 or 755: Git actually only pays
|
||
attention to the executable bit.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="blob-object"></a>Blob Object</h2></div></div></div><p>You can use git-show(1) to examine the contents of a blob; take,
|
||
for example, the blob in the entry for <code class="literal">COPYING</code> from the tree above:</p><pre class="screen">$ git show 6ff87c4664
|
||
|
||
Note that the only valid version of the GPL as far as this project
|
||
is concerned is _this_ particular version of the license (ie v2, not
|
||
v2.2 or v3.x or whatever), unless explicitly otherwise stated.
|
||
...</pre><p>A "blob" object is nothing but a binary blob of data. It doesn’t refer
|
||
to anything else or have attributes of any kind.</p><p>Since the blob is entirely defined by its data, if two files in a
|
||
directory tree (or in multiple different versions of the repository)
|
||
have the same contents, they will share the same blob object. The object
|
||
is totally independent of its location in the directory tree, and
|
||
renaming a file does not change the object that file is associated with.</p><p>Note that any tree or blob object can be examined using
|
||
git-show(1) with the <revision>:<path> syntax. This can
|
||
sometimes be useful for browsing the contents of a tree that is not
|
||
currently checked out.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="trust"></a>Trust</h2></div></div></div><p>If you receive the SHA-1 name of a blob from one source, and its contents
|
||
from another (possibly untrusted) source, you can still trust that those
|
||
contents are correct as long as the SHA-1 name agrees. This is because
|
||
the SHA-1 is designed so that it is infeasible to find different contents
|
||
that produce the same hash.</p><p>Similarly, you need only trust the SHA-1 name of a top-level tree object
|
||
to trust the contents of the entire directory that it refers to, and if
|
||
you receive the SHA-1 name of a commit from a trusted source, then you
|
||
can easily verify the entire history of commits reachable through
|
||
parents of that commit, and all of those contents of the trees referred
|
||
to by those commits.</p><p>So to introduce some real trust in the system, the only thing you need
|
||
to do is to digitally sign just <span class="emphasis"><em>one</em></span> special note, which includes the
|
||
name of a top-level commit. Your digital signature shows others
|
||
that you trust that commit, and the immutability of the history of
|
||
commits tells others that they can trust the whole history.</p><p>In other words, you can easily validate a whole archive by just
|
||
sending out a single email that tells the people the name (SHA-1 hash)
|
||
of the top commit, and digitally sign that email using something
|
||
like GPG/PGP.</p><p>To assist in this, Git also provides the tag object…</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="tag-object"></a>Tag Object</h2></div></div></div><p>A tag object contains an object, object type, tag name, the name of the
|
||
person ("tagger") who created the tag, and a message, which may contain
|
||
a signature, as can be seen using git-cat-file(1):</p><pre class="screen">$ git cat-file tag v1.5.0
|
||
object 437b1b20df4b356c9342dac8d38849f24ef44f27
|
||
type commit
|
||
tag v1.5.0
|
||
tagger Junio C Hamano <junkio@cox.net> 1171411200 +0000
|
||
|
||
GIT 1.5.0
|
||
-----BEGIN PGP SIGNATURE-----
|
||
Version: GnuPG v1.4.6 (GNU/Linux)
|
||
|
||
iD8DBQBF0lGqwMbZpPMRm5oRAuRiAJ9ohBLd7s2kqjkKlq1qqC57SbnmzQCdG4ui
|
||
nLE/L9aUXdWeTFPron96DLA=
|
||
=2E+0
|
||
-----END PGP SIGNATURE-----</pre><p>See the git-tag(1) command to learn how to create and verify tag
|
||
objects. (Note that git-tag(1) can also be used to create
|
||
"lightweight tags", which are not tag objects at all, but just simple
|
||
references whose names begin with <code class="literal">refs/tags/</code>).</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="pack-files"></a>How Git stores objects efficiently: pack files</h2></div></div></div><p>Newly created objects are initially created in a file named after the
|
||
object’s SHA-1 hash (stored in <code class="literal">.git/objects</code>).</p><p>Unfortunately this system becomes inefficient once a project has a
|
||
lot of objects. Try this on an old project:</p><pre class="screen">$ git count-objects
|
||
6930 objects, 47620 kilobytes</pre><p>The first number is the number of objects which are kept in
|
||
individual files. The second is the amount of space taken up by
|
||
those "loose" objects.</p><p>You can save space and make Git faster by moving these loose objects in
|
||
to a "pack file", which stores a group of objects in an efficient
|
||
compressed format; the details of how pack files are formatted can be
|
||
found in <a class="ulink" href="technical/pack-format.html" target="_top">pack format</a>.</p><p>To put the loose objects into a pack, just run git repack:</p><pre class="screen">$ git repack
|
||
Counting objects: 6020, done.
|
||
Delta compression using up to 4 threads.
|
||
Compressing objects: 100% (6020/6020), done.
|
||
Writing objects: 100% (6020/6020), done.
|
||
Total 6020 (delta 4070), reused 0 (delta 0)</pre><p>This creates a single "pack file" in .git/objects/pack/
|
||
containing all currently unpacked objects. You can then run</p><pre class="screen">$ git prune</pre><p>to remove any of the "loose" objects that are now contained in the
|
||
pack. This will also remove any unreferenced objects (which may be
|
||
created when, for example, you use <code class="literal">git reset</code> to remove a commit).
|
||
You can verify that the loose objects are gone by looking at the
|
||
<code class="literal">.git/objects</code> directory or by running</p><pre class="screen">$ git count-objects
|
||
0 objects, 0 kilobytes</pre><p>Although the object files are gone, any commands that refer to those
|
||
objects will work exactly as they did before.</p><p>The git-gc(1) command performs packing, pruning, and more for
|
||
you, so is normally the only high-level command you need.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="dangling-objects"></a>Dangling objects</h2></div></div></div><p>The git-fsck(1) command will sometimes complain about dangling
|
||
objects. They are not a problem.</p><p>The most common cause of dangling objects is that you’ve rebased a
|
||
branch, or you have pulled from somebody else who rebased a branch—see
|
||
<a class="xref" href="#cleaning-up-history" title="Part V. Rewriting history and maintaining patch series">Part V, “Rewriting history and maintaining patch series”</a>. In that case, the old head of the original
|
||
branch still exists, as does everything it pointed to. The branch
|
||
pointer itself just doesn’t, since you replaced it with another one.</p><p>There are also other situations that cause dangling objects. For
|
||
example, a "dangling blob" may arise because you did a <code class="literal">git add</code> of a
|
||
file, but then, before you actually committed it and made it part of the
|
||
bigger picture, you changed something else in that file and committed
|
||
that <span class="strong"><strong>updated</strong></span> thing—the old state that you added originally ends up
|
||
not being pointed to by any commit or tree, so it’s now a dangling blob
|
||
object.</p><p>Similarly, when the "recursive" merge strategy runs, and finds that
|
||
there are criss-cross merges and thus more than one merge base (which is
|
||
fairly unusual, but it does happen), it will generate one temporary
|
||
midway tree (or possibly even more, if you had lots of criss-crossing
|
||
merges and more than two merge bases) as a temporary internal merge
|
||
base, and again, those are real objects, but the end result will not end
|
||
up pointing to them, so they end up "dangling" in your repository.</p><p>Generally, dangling objects aren’t anything to worry about. They can
|
||
even be very useful: if you screw something up, the dangling objects can
|
||
be how you recover your old tree (say, you did a rebase, and realized
|
||
that you really didn’t want to—you can look at what dangling objects
|
||
you have, and decide to reset your head to some old dangling state).</p><p>For commits, you can just use:</p><pre class="screen">$ gitk <dangling-commit-sha-goes-here> --not --all</pre><p>This asks for all the history reachable from the given commit but not
|
||
from any branch, tag, or other reference. If you decide it’s something
|
||
you want, you can always create a new reference to it, e.g.,</p><pre class="screen">$ git branch recovered-branch <dangling-commit-sha-goes-here></pre><p>For blobs and trees, you can’t do the same, but you can still examine
|
||
them. You can just do</p><pre class="screen">$ git show <dangling-blob/tree-sha-goes-here></pre><p>to show what the contents of the blob were (or, for a tree, basically
|
||
what the <code class="literal">ls</code> for that directory was), and that may give you some idea
|
||
of what the operation was that left that dangling object.</p><p>Usually, dangling blobs and trees aren’t very interesting. They’re
|
||
almost always the result of either being a half-way mergebase (the blob
|
||
will often even have the conflict markers from a merge in it, if you
|
||
have had conflicting merges that you fixed up by hand), or simply
|
||
because you interrupted a <code class="literal">git fetch</code> with ^C or something like that,
|
||
leaving <span class="emphasis"><em>some</em></span> of the new objects in the object database, but just
|
||
dangling and useless.</p><p>Anyway, once you are sure that you’re not interested in any dangling
|
||
state, you can just prune all unreachable objects:</p><pre class="screen">$ git prune</pre><p>and they’ll be gone. (You should only run <code class="literal">git prune</code> on a quiescent
|
||
repository—it’s kind of like doing a filesystem fsck recovery: you
|
||
don’t want to do that while the filesystem is mounted.
|
||
<code class="literal">git prune</code> is designed not to cause any harm in such cases of concurrent
|
||
accesses to a repository but you might receive confusing or scary messages.)</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="recovering-from-repository-corruption"></a>Recovering from repository corruption</h2></div></div></div><p>By design, Git treats data trusted to it with caution. However, even in
|
||
the absence of bugs in Git itself, it is still possible that hardware or
|
||
operating system errors could corrupt data.</p><p>The first defense against such problems is backups. You can back up a
|
||
Git directory using clone, or just using cp, tar, or any other backup
|
||
mechanism.</p><p>As a last resort, you can search for the corrupted objects and attempt
|
||
to replace them by hand. Back up your repository before attempting this
|
||
in case you corrupt things even more in the process.</p><p>We’ll assume that the problem is a single missing or corrupted blob,
|
||
which is sometimes a solvable problem. (Recovering missing trees and
|
||
especially commits is <span class="strong"><strong>much</strong></span> harder).</p><p>Before starting, verify that there is corruption, and figure out where
|
||
it is with git-fsck(1); this may be time-consuming.</p><p>Assume the output looks like this:</p><pre class="screen">$ git fsck --full --no-dangling
|
||
broken link from tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8
|
||
to blob 4b9458b3786228369c63936db65827de3cc06200
|
||
missing blob 4b9458b3786228369c63936db65827de3cc06200</pre><p>Now you know that blob 4b9458b3 is missing, and that the tree 2d9263c6
|
||
points to it. If you could find just one copy of that missing blob
|
||
object, possibly in some other repository, you could move it into
|
||
<code class="literal">.git/objects/4b/9458b3...</code> and be done. Suppose you can’t. You can
|
||
still examine the tree that pointed to it with git-ls-tree(1),
|
||
which might output something like:</p><pre class="screen">$ git ls-tree 2d9263c6d23595e7cb2a21e5ebbb53655278dff8
|
||
100644 blob 8d14531846b95bfa3564b58ccfb7913a034323b8 .gitignore
|
||
100644 blob ebf9bf84da0aab5ed944264a5db2a65fe3a3e883 .mailmap
|
||
100644 blob ca442d313d86dc67e0a2e5d584b465bd382cbf5c COPYING
|
||
...
|
||
100644 blob 4b9458b3786228369c63936db65827de3cc06200 myfile
|
||
...</pre><p>So now you know that the missing blob was the data for a file named
|
||
<code class="literal">myfile</code>. And chances are you can also identify the directory—let’s
|
||
say it’s in <code class="literal">somedirectory</code>. If you’re lucky the missing copy might be
|
||
the same as the copy you have checked out in your working tree at
|
||
<code class="literal">somedirectory/myfile</code>; you can test whether that’s right with
|
||
git-hash-object(1):</p><pre class="screen">$ git hash-object -w somedirectory/myfile</pre><p>which will create and store a blob object with the contents of
|
||
somedirectory/myfile, and output the SHA-1 of that object. if you’re
|
||
extremely lucky it might be 4b9458b3786228369c63936db65827de3cc06200, in
|
||
which case you’ve guessed right, and the corruption is fixed!</p><p>Otherwise, you need more information. How do you tell which version of
|
||
the file has been lost?</p><p>The easiest way to do this is with:</p><pre class="screen">$ git log --raw --all --full-history -- somedirectory/myfile</pre><p>Because you’re asking for raw output, you’ll now get something like</p><pre class="screen">commit abc
|
||
Author:
|
||
Date:
|
||
...
|
||
:100644 100644 4b9458b newsha M somedirectory/myfile
|
||
|
||
|
||
commit xyz
|
||
Author:
|
||
Date:
|
||
|
||
...
|
||
:100644 100644 oldsha 4b9458b M somedirectory/myfile</pre><p>This tells you that the immediately following version of the file was
|
||
"newsha", and that the immediately preceding version was "oldsha".
|
||
You also know the commit messages that went with the change from oldsha
|
||
to 4b9458b and with the change from 4b9458b to newsha.</p><p>If you’ve been committing small enough changes, you may now have a good
|
||
shot at reconstructing the contents of the in-between state 4b9458b.</p><p>If you can do that, you can now recreate the missing object with</p><pre class="screen">$ git hash-object -w <recreated-file></pre><p>and your repository is good again!</p><p>(Btw, you could have ignored the <code class="literal">fsck</code>, and started with doing a</p><pre class="screen">$ git log --raw --all</pre><p>and just looked for the sha of the missing object (4b9458b) in that
|
||
whole thing. It’s up to you—Git does <span class="strong"><strong>have</strong></span> a lot of information, it is
|
||
just missing one particular blob version.</p></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="the-index"></a>Chapter 48. The index</h2></div></div></div><p>The index is a binary file (generally kept in <code class="literal">.git/index</code>) containing a
|
||
sorted list of path names, each with permissions and the SHA-1 of a blob
|
||
object; git-ls-files(1) can show you the contents of the index:</p><pre class="screen">$ git ls-files --stage
|
||
100644 63c918c667fa005ff12ad89437f2fdc80926e21c 0 .gitignore
|
||
100644 5529b198e8d14decbe4ad99db3f7fb632de0439d 0 .mailmap
|
||
100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 0 COPYING
|
||
100644 a37b2152bd26be2c2289e1f57a292534a51a93c7 0 Documentation/.gitignore
|
||
100644 fbefe9a45b00a54b58d94d06eca48b03d40a50e0 0 Documentation/Makefile
|
||
...
|
||
100644 2511aef8d89ab52be5ec6a5e46236b4b6bcd07ea 0 xdiff/xtypes.h
|
||
100644 2ade97b2574a9f77e7ae4002a4e07a6a38e46d07 0 xdiff/xutils.c
|
||
100644 d5de8292e05e7c36c4b68857c1cf9855e3d2f70a 0 xdiff/xutils.h</pre><p>Note that in older documentation you may see the index called the
|
||
"current directory cache" or just the "cache". It has three important
|
||
properties:</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p class="simpara">The index contains all the information necessary to generate a single
|
||
(uniquely determined) tree object.</p><p class="simpara">For example, running git-commit(1) generates this tree object
|
||
from the index, stores it in the object database, and uses it as the
|
||
tree object associated with the new commit.</p></li><li class="listitem"><p class="simpara">The index enables fast comparisons between the tree object it defines
|
||
and the working tree.</p><p class="simpara">It does this by storing some additional data for each entry (such as
|
||
the last modified time). This data is not displayed above, and is not
|
||
stored in the created tree object, but it can be used to determine
|
||
quickly which files in the working directory differ from what was
|
||
stored in the index, and thus save Git from having to read all of the
|
||
data from such files to look for changes.</p></li><li class="listitem"><p class="simpara">It can efficiently represent information about merge conflicts
|
||
between different tree objects, allowing each pathname to be
|
||
associated with sufficient information about the trees involved that
|
||
you can create a three-way merge between them.</p><p class="simpara">We saw in <a class="xref" href="#conflict-resolution" title="Getting conflict-resolution help during a merge">the section called “Getting conflict-resolution help during a merge”</a> that during a merge the index can
|
||
store multiple versions of a single file (called "stages"). The third
|
||
column in the git-ls-files(1) output above is the stage
|
||
number, and will take on values other than 0 for files with merge
|
||
conflicts.</p></li></ol></div><p>The index is thus a sort of temporary staging area, which is filled with
|
||
a tree which you are in the process of working on.</p><p>If you blow the index away entirely, you generally haven’t lost any
|
||
information as long as you have the name of the tree that it described.</p></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="submodules"></a>Part VIII. Submodules</h1></div></div></div><div class="partintro"><div></div><p>Large projects are often composed of smaller, self-contained modules. For
|
||
example, an embedded Linux distribution’s source tree would include every
|
||
piece of software in the distribution with some local modifications; a movie
|
||
player might need to build against a specific, known-working version of a
|
||
decompression library; several independent programs might all share the same
|
||
build scripts.</p><p>With centralized revision control systems this is often accomplished by
|
||
including every module in one single repository. Developers can check out
|
||
all modules or only the modules they need to work with. They can even modify
|
||
files across several modules in a single commit while moving things around
|
||
or updating APIs and translations.</p><p>Git does not allow partial checkouts, so duplicating this approach in Git
|
||
would force developers to keep a local copy of modules they are not
|
||
interested in touching. Commits in an enormous checkout would be slower
|
||
than you’d expect as Git would have to scan every directory for changes.
|
||
If modules have a lot of local history, clones would take forever.</p><p>On the plus side, distributed revision control systems can much better
|
||
integrate with external sources. In a centralized model, a single arbitrary
|
||
snapshot of the external project is exported from its own revision control
|
||
and then imported into the local revision control on a vendor branch. All
|
||
the history is hidden. With distributed revision control you can clone the
|
||
entire external history and much more easily follow development and re-merge
|
||
local changes.</p><p>Git’s submodule support allows a repository to contain, as a subdirectory, a
|
||
checkout of an external project. Submodules maintain their own identity;
|
||
the submodule support just stores the submodule repository location and
|
||
commit ID, so other developers who clone the containing project
|
||
("superproject") can easily clone all the submodules at the same revision.
|
||
Partial checkouts of the superproject are possible: you can tell Git to
|
||
clone none, some or all of the submodules.</p><p>The git-submodule(1) command is available since Git 1.5.3. Users
|
||
with Git 1.5.2 can look up the submodule commits in the repository and
|
||
manually check them out; earlier versions won’t recognize the submodules at
|
||
all.</p><p>To see how submodule support works, create four example
|
||
repositories that can be used later as a submodule:</p><pre class="screen">$ mkdir ~/git
|
||
$ cd ~/git
|
||
$ for i in a b c d
|
||
do
|
||
mkdir $i
|
||
cd $i
|
||
git init
|
||
echo "module $i" > $i.txt
|
||
git add $i.txt
|
||
git commit -m "Initial commit, submodule $i"
|
||
cd ..
|
||
done</pre><p>Now create the superproject and add all the submodules:</p><pre class="screen">$ mkdir super
|
||
$ cd super
|
||
$ git init
|
||
$ for i in a b c d
|
||
do
|
||
git submodule add ~/git/$i $i
|
||
done</pre><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>Do not use local URLs here if you plan to publish your superproject!</p></div><p>See what files <code class="literal">git submodule</code> created:</p><pre class="screen">$ ls -a
|
||
. .. .git .gitmodules a b c d</pre><p>The <code class="literal">git submodule add <repo> <path></code> command does a couple of things:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">It clones the submodule from <code class="literal"><repo></code> to the given <code class="literal"><path></code> under the
|
||
current directory and by default checks out the master branch.</li><li class="listitem">It adds the submodule’s clone path to the gitmodules(5) file and
|
||
adds this file to the index, ready to be committed.</li><li class="listitem">It adds the submodule’s current commit ID to the index, ready to be
|
||
committed.</li></ul></div><p>Commit the superproject:</p><pre class="screen">$ git commit -m "Add submodules a, b, c and d."</pre><p>Now clone the superproject:</p><pre class="screen">$ cd ..
|
||
$ git clone super cloned
|
||
$ cd cloned</pre><p>The submodule directories are there, but they’re empty:</p><pre class="screen">$ ls -a a
|
||
. ..
|
||
$ git submodule status
|
||
-d266b9873ad50488163457f025db7cdd9683d88b a
|
||
-e81d457da15309b4fef4249aba9b50187999670d b
|
||
-c1536a972b9affea0f16e0680ba87332dc059146 c
|
||
-d96249ff5d57de5de093e6baff9e0aafa5276a74 d</pre><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>The commit object names shown above would be different for you, but they
|
||
should match the HEAD commit object names of your repositories. You can check
|
||
it by running <code class="literal">git ls-remote ../a</code>.</p></div><p>Pulling down the submodules is a two-step process. First run <code class="literal">git submodule
|
||
init</code> to add the submodule repository URLs to <code class="literal">.git/config</code>:</p><pre class="screen">$ git submodule init</pre><p>Now use <code class="literal">git submodule update</code> to clone the repositories and check out the
|
||
commits specified in the superproject:</p><pre class="screen">$ git submodule update
|
||
$ cd a
|
||
$ ls -a
|
||
. .. .git a.txt</pre><p>One major difference between <code class="literal">git submodule update</code> and <code class="literal">git submodule add</code> is
|
||
that <code class="literal">git submodule update</code> checks out a specific commit, rather than the tip
|
||
of a branch. It’s like checking out a tag: the head is detached, so you’re not
|
||
working on a branch.</p><pre class="screen">$ git branch
|
||
* (detached from d266b98)
|
||
master</pre><p>If you want to make a change within a submodule and you have a detached head,
|
||
then you should create or checkout a branch, make your changes, publish the
|
||
change within the submodule, and then update the superproject to reference the
|
||
new commit:</p><pre class="screen">$ git checkout master</pre><p>or</p><pre class="screen">$ git checkout -b fix-up</pre><p>then</p><pre class="screen">$ echo "adding a line again" >> a.txt
|
||
$ git commit -a -m "Updated the submodule from within the superproject."
|
||
$ git push
|
||
$ cd ..
|
||
$ git diff
|
||
diff --git a/a b/a
|
||
index d266b98..261dfac 160000
|
||
--- a/a
|
||
+++ b/a
|
||
@@ -1 +1 @@
|
||
-Subproject commit d266b9873ad50488163457f025db7cdd9683d88b
|
||
+Subproject commit 261dfac35cb99d380eb966e102c1197139f7fa24
|
||
$ git add a
|
||
$ git commit -m "Updated submodule a."
|
||
$ git push</pre><p>You have to run <code class="literal">git submodule update</code> after <code class="literal">git pull</code> if you want to update
|
||
submodules, too.</p><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#_pitfalls_with_submodules">49. Pitfalls with submodules</a></span></dt></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="_pitfalls_with_submodules"></a>Chapter 49. Pitfalls with submodules</h2></div></div></div><p>Always publish the submodule change before publishing the change to the
|
||
superproject that references it. If you forget to publish the submodule change,
|
||
others won’t be able to clone the repository:</p><pre class="screen">$ cd ~/git/super/a
|
||
$ echo i added another line to this file >> a.txt
|
||
$ git commit -a -m "doing it wrong this time"
|
||
$ cd ..
|
||
$ git add a
|
||
$ git commit -m "Updated submodule a again."
|
||
$ git push
|
||
$ cd ~/git/cloned
|
||
$ git pull
|
||
$ git submodule update
|
||
error: pathspec '261dfac35cb99d380eb966e102c1197139f7fa24' did not match any file(s) known to git.
|
||
Did you forget to 'git add'?
|
||
Unable to checkout '261dfac35cb99d380eb966e102c1197139f7fa24' in submodule path 'a'</pre><p>In older Git versions it could be easily forgotten to commit new or modified
|
||
files in a submodule, which silently leads to similar problems as not pushing
|
||
the submodule changes. Starting with Git 1.7.0 both <code class="literal">git status</code> and <code class="literal">git diff</code>
|
||
in the superproject show submodules as modified when they contain new or
|
||
modified files to protect against accidentally committing such a state. <code class="literal">git
|
||
diff</code> will also add a <code class="literal">-dirty</code> to the work tree side when generating patch
|
||
output or used with the <code class="literal">--submodule</code> option:</p><pre class="screen">$ git diff
|
||
diff --git a/sub b/sub
|
||
--- a/sub
|
||
+++ b/sub
|
||
@@ -1 +1 @@
|
||
-Subproject commit 3f356705649b5d566d97ff843cf193359229a453
|
||
+Subproject commit 3f356705649b5d566d97ff843cf193359229a453-dirty
|
||
$ git diff --submodule
|
||
Submodule sub 3f35670..3f35670-dirty:</pre><p>You also should not rewind branches in a submodule beyond commits that were
|
||
ever recorded in any superproject.</p><p>It’s not safe to run <code class="literal">git submodule update</code> if you’ve made and committed
|
||
changes within a submodule without checking out a branch first. They will be
|
||
silently overwritten:</p><pre class="screen">$ cat a.txt
|
||
module a
|
||
$ echo line added from private2 >> a.txt
|
||
$ git commit -a -m "line added inside private2"
|
||
$ cd ..
|
||
$ git submodule update
|
||
Submodule path 'a': checked out 'd266b9873ad50488163457f025db7cdd9683d88b'
|
||
$ cd a
|
||
$ cat a.txt
|
||
module a</pre><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p>The changes are still visible in the submodule’s reflog.</p></div><p>If you have uncommitted changes in your submodule working tree, <code class="literal">git
|
||
submodule update</code> will not overwrite them. Instead, you get the usual
|
||
warning about not being able switch from a dirty branch.</p></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="low-level-operations"></a>Part IX. Low-level Git operations</h1></div></div></div><div class="partintro"><div></div><p>Many of the higher-level commands were originally implemented as shell
|
||
scripts using a smaller core of low-level Git commands. These can still
|
||
be useful when doing unusual things with Git, or just as a way to
|
||
understand its inner workings.</p><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#object-manipulation">50. Object access and manipulation</a></span></dt><dt><span class="chapter"><a href="#the-workflow">51. The Workflow</a></span></dt><dd><dl><dt><span class="section"><a href="#working-directory-to-index">working directory → index</a></span></dt><dt><span class="section"><a href="#index-to-object-database">index → object database</a></span></dt><dt><span class="section"><a href="#object-database-to-index">object database → index</a></span></dt><dt><span class="section"><a href="#index-to-working-directory">index → working directory</a></span></dt><dt><span class="section"><a href="#tying-it-all-together">Tying it all together</a></span></dt></dl></dd><dt><span class="chapter"><a href="#examining-the-data">52. Examining the data</a></span></dt><dt><span class="chapter"><a href="#merging-multiple-trees">53. Merging multiple trees</a></span></dt><dt><span class="chapter"><a href="#merging-multiple-trees-2">54. Merging multiple trees, continued</a></span></dt></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="object-manipulation"></a>Chapter 50. Object access and manipulation</h2></div></div></div><p>The git-cat-file(1) command can show the contents of any object,
|
||
though the higher-level git-show(1) is usually more useful.</p><p>The git-commit-tree(1) command allows constructing commits with
|
||
arbitrary parents and trees.</p><p>A tree can be created with git-write-tree(1) and its data can be
|
||
accessed by git-ls-tree(1). Two trees can be compared with
|
||
git-diff-tree(1).</p><p>A tag is created with git-mktag(1), and the signature can be
|
||
verified by git-verify-tag(1), though it is normally simpler to
|
||
use git-tag(1) for both.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="the-workflow"></a>Chapter 51. The Workflow</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="section"><a href="#working-directory-to-index">working directory → index</a></span></dt><dt><span class="section"><a href="#index-to-object-database">index → object database</a></span></dt><dt><span class="section"><a href="#object-database-to-index">object database → index</a></span></dt><dt><span class="section"><a href="#index-to-working-directory">index → working directory</a></span></dt><dt><span class="section"><a href="#tying-it-all-together">Tying it all together</a></span></dt></dl></div><p>High-level operations such as git-commit(1),
|
||
git-checkout(1) and git-reset(1) work by moving data
|
||
between the working tree, the index, and the object database. Git
|
||
provides low-level operations which perform each of these steps
|
||
individually.</p><p>Generally, all Git operations work on the index file. Some operations
|
||
work <span class="strong"><strong>purely</strong></span> on the index file (showing the current state of the
|
||
index), but most operations move data between the index file and either
|
||
the database or the working directory. Thus there are four main
|
||
combinations:</p><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="working-directory-to-index"></a>working directory → index</h2></div></div></div><p>The git-update-index(1) command updates the index with
|
||
information from the working directory. You generally update the
|
||
index information by just specifying the filename you want to update,
|
||
like so:</p><pre class="screen">$ git update-index filename</pre><p>but to avoid common mistakes with filename globbing etc., the command
|
||
will not normally add totally new entries or remove old entries,
|
||
i.e. it will normally just update existing cache entries.</p><p>To tell Git that yes, you really do realize that certain files no
|
||
longer exist, or that new files should be added, you
|
||
should use the <code class="literal">--remove</code> and <code class="literal">--add</code> flags respectively.</p><p>NOTE! A <code class="literal">--remove</code> flag does <span class="emphasis"><em>not</em></span> mean that subsequent filenames will
|
||
necessarily be removed: if the files still exist in your directory
|
||
structure, the index will be updated with their new status, not
|
||
removed. The only thing <code class="literal">--remove</code> means is that update-index will be
|
||
considering a removed file to be a valid thing, and if the file really
|
||
does not exist any more, it will update the index accordingly.</p><p>As a special case, you can also do <code class="literal">git update-index --refresh</code>, which
|
||
will refresh the "stat" information of each index to match the current
|
||
stat information. It will <span class="emphasis"><em>not</em></span> update the object status itself, and
|
||
it will only update the fields that are used to quickly test whether
|
||
an object still matches its old backing store object.</p><p>The previously introduced git-add(1) is just a wrapper for
|
||
git-update-index(1).</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="index-to-object-database"></a>index → object database</h2></div></div></div><p>You write your current index file to a "tree" object with the program</p><pre class="screen">$ git write-tree</pre><p>that doesn’t come with any options—it will just write out the
|
||
current index into the set of tree objects that describe that state,
|
||
and it will return the name of the resulting top-level tree. You can
|
||
use that tree to re-generate the index at any time by going in the
|
||
other direction:</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="object-database-to-index"></a>object database → index</h2></div></div></div><p>You read a "tree" file from the object database, and use that to
|
||
populate (and overwrite—don’t do this if your index contains any
|
||
unsaved state that you might want to restore later!) your current
|
||
index. Normal operation is just</p><pre class="screen">$ git read-tree <SHA-1 of tree></pre><p>and your index file will now be equivalent to the tree that you saved
|
||
earlier. However, that is only your <span class="emphasis"><em>index</em></span> file: your working
|
||
directory contents have not been modified.</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="index-to-working-directory"></a>index → working directory</h2></div></div></div><p>You update your working directory from the index by "checking out"
|
||
files. This is not a very common operation, since normally you’d just
|
||
keep your files updated, and rather than write to your working
|
||
directory, you’d tell the index files about the changes in your
|
||
working directory (i.e. <code class="literal">git update-index</code>).</p><p>However, if you decide to jump to a new version, or check out somebody
|
||
else’s version, or just restore a previous tree, you’d populate your
|
||
index file with read-tree, and then you need to check out the result
|
||
with</p><pre class="screen">$ git checkout-index filename</pre><p>or, if you want to check out all of the index, use <code class="literal">-a</code>.</p><p>NOTE! <code class="literal">git checkout-index</code> normally refuses to overwrite old files, so
|
||
if you have an old version of the tree already checked out, you will
|
||
need to use the <code class="literal">-f</code> flag (<span class="emphasis"><em>before</em></span> the <code class="literal">-a</code> flag or the filename) to
|
||
<span class="emphasis"><em>force</em></span> the checkout.</p><p>Finally, there are a few odds and ends which are not purely moving
|
||
from one representation to the other:</p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="tying-it-all-together"></a>Tying it all together</h2></div></div></div><p>To commit a tree you have instantiated with <code class="literal">git write-tree</code>, you’d
|
||
create a "commit" object that refers to that tree and the history
|
||
behind it—most notably the "parent" commits that preceded it in
|
||
history.</p><p>Normally a "commit" has one parent: the previous state of the tree
|
||
before a certain change was made. However, sometimes it can have two
|
||
or more parent commits, in which case we call it a "merge", due to the
|
||
fact that such a commit brings together ("merges") two or more
|
||
previous states represented by other commits.</p><p>In other words, while a "tree" represents a particular directory state
|
||
of a working directory, a "commit" represents that state in time,
|
||
and explains how we got there.</p><p>You create a commit object by giving it the tree that describes the
|
||
state at the time of the commit, and a list of parents:</p><pre class="screen">$ git commit-tree <tree> -p <parent> [(-p <parent2>)...]</pre><p>and then giving the reason for the commit on stdin (either through
|
||
redirection from a pipe or file, or by just typing it at the tty).</p><p><code class="literal">git commit-tree</code> will return the name of the object that represents
|
||
that commit, and you should save it away for later use. Normally,
|
||
you’d commit a new <code class="literal">HEAD</code> state, and while Git doesn’t care where you
|
||
save the note about that state, in practice we tend to just write the
|
||
result to the file pointed at by <code class="literal">.git/HEAD</code>, so that we can always see
|
||
what the last committed state was.</p><p>Here is a picture that illustrates how various pieces fit together:</p><pre class="screen"> commit-tree
|
||
commit obj
|
||
+----+
|
||
| |
|
||
| |
|
||
V V
|
||
+-----------+
|
||
| Object DB |
|
||
| Backing |
|
||
| Store |
|
||
+-----------+
|
||
^
|
||
write-tree | |
|
||
tree obj | |
|
||
| | read-tree
|
||
| | tree obj
|
||
V
|
||
+-----------+
|
||
| Index |
|
||
| "cache" |
|
||
+-----------+
|
||
update-index ^
|
||
blob obj | |
|
||
| |
|
||
checkout-index -u | | checkout-index
|
||
stat | | blob obj
|
||
V
|
||
+-----------+
|
||
| Working |
|
||
| Directory |
|
||
+-----------+</pre></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="examining-the-data"></a>Chapter 52. Examining the data</h2></div></div></div><p>You can examine the data represented in the object database and the
|
||
index with various helper tools. For every object, you can use
|
||
git-cat-file(1) to examine details about the
|
||
object:</p><pre class="screen">$ git cat-file -t <objectname></pre><p>shows the type of the object, and once you have the type (which is
|
||
usually implicit in where you find the object), you can use</p><pre class="screen">$ git cat-file blob|tree|commit|tag <objectname></pre><p>to show its contents. NOTE! Trees have binary content, and as a result
|
||
there is a special helper for showing that content, called
|
||
<code class="literal">git ls-tree</code>, which turns the binary content into a more easily
|
||
readable form.</p><p>It’s especially instructive to look at "commit" objects, since those
|
||
tend to be small and fairly self-explanatory. In particular, if you
|
||
follow the convention of having the top commit name in <code class="literal">.git/HEAD</code>,
|
||
you can do</p><pre class="screen">$ git cat-file commit HEAD</pre><p>to see what the top commit was.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="merging-multiple-trees"></a>Chapter 53. Merging multiple trees</h2></div></div></div><p>Git can help you perform a three-way merge, which can in turn be
|
||
used for a many-way merge by repeating the merge procedure several
|
||
times. The usual situation is that you only do one three-way merge
|
||
(reconciling two lines of history) and commit the result, but if
|
||
you like to, you can merge several branches in one go.</p><p>To perform a three-way merge, you start with the two commits you
|
||
want to merge, find their closest common parent (a third commit),
|
||
and compare the trees corresponding to these three commits.</p><p>To get the "base" for the merge, look up the common parent of two
|
||
commits:</p><pre class="screen">$ git merge-base <commit1> <commit2></pre><p>This prints the name of a commit they are both based on. You should
|
||
now look up the tree objects of those commits, which you can easily
|
||
do with</p><pre class="screen">$ git cat-file commit <commitname> | head -1</pre><p>since the tree object information is always the first line in a commit
|
||
object.</p><p>Once you know the three trees you are going to merge (the one "original"
|
||
tree, aka the common tree, and the two "result" trees, aka the branches
|
||
you want to merge), you do a "merge" read into the index. This will
|
||
complain if it has to throw away your old index contents, so you should
|
||
make sure that you’ve committed those—in fact you would normally
|
||
always do a merge against your last commit (which should thus match what
|
||
you have in your current index anyway).</p><p>To do the merge, do</p><pre class="screen">$ git read-tree -m -u <origtree> <yourtree> <targettree></pre><p>which will do all trivial merge operations for you directly in the
|
||
index file, and you can just write the result out with
|
||
<code class="literal">git write-tree</code>.</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="merging-multiple-trees-2"></a>Chapter 54. Merging multiple trees, continued</h2></div></div></div><p>Sadly, many merges aren’t trivial. If there are files that have
|
||
been added, moved or removed, or if both branches have modified the
|
||
same file, you will be left with an index tree that contains "merge
|
||
entries" in it. Such an index tree can <span class="emphasis"><em>NOT</em></span> be written out to a tree
|
||
object, and you will have to resolve any such merge clashes using
|
||
other tools before you can write out the result.</p><p>You can examine such index state with <code class="literal">git ls-files --unmerged</code>
|
||
command. An example:</p><pre class="screen">$ git read-tree -m $orig HEAD $target
|
||
$ git ls-files --unmerged
|
||
100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c
|
||
100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c
|
||
100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c</pre><p>Each line of the <code class="literal">git ls-files --unmerged</code> output begins with
|
||
the blob mode bits, blob SHA-1, <span class="emphasis"><em>stage number</em></span>, and the
|
||
filename. The <span class="emphasis"><em>stage number</em></span> is Git’s way to say which tree it
|
||
came from: stage 1 corresponds to the <code class="literal">$orig</code> tree, stage 2 to
|
||
the <code class="literal">HEAD</code> tree, and stage 3 to the <code class="literal">$target</code> tree.</p><p>Earlier we said that trivial merges are done inside
|
||
<code class="literal">git read-tree -m</code>. For example, if the file did not change
|
||
from <code class="literal">$orig</code> to <code class="literal">HEAD</code> or <code class="literal">$target</code>, or if the file changed
|
||
from <code class="literal">$orig</code> to <code class="literal">HEAD</code> and <code class="literal">$orig</code> to <code class="literal">$target</code> the same way,
|
||
obviously the final outcome is what is in <code class="literal">HEAD</code>. What the
|
||
above example shows is that file <code class="literal">hello.c</code> was changed from
|
||
<code class="literal">$orig</code> to <code class="literal">HEAD</code> and <code class="literal">$orig</code> to <code class="literal">$target</code> in a different way.
|
||
You could resolve this by running your favorite 3-way merge
|
||
program, e.g. <code class="literal">diff3</code>, <code class="literal">merge</code>, or Git’s own merge-file, on
|
||
the blob objects from these three stages yourself, like this:</p><pre class="screen">$ git cat-file blob 263414f >hello.c~1
|
||
$ git cat-file blob 06fa6a2 >hello.c~2
|
||
$ git cat-file blob cc44c73 >hello.c~3
|
||
$ git merge-file hello.c~2 hello.c~1 hello.c~3</pre><p>This would leave the merge result in <code class="literal">hello.c~2</code> file, along
|
||
with conflict markers if there are conflicts. After verifying
|
||
the merge result makes sense, you can tell Git what the final
|
||
merge result for this file is by:</p><pre class="screen">$ mv -f hello.c~2 hello.c
|
||
$ git update-index hello.c</pre><p>When a path is in the "unmerged" state, running <code class="literal">git update-index</code> for
|
||
that path tells Git to mark the path resolved.</p><p>The above is the description of a Git merge at the lowest level,
|
||
to help you understand what conceptually happens under the hood.
|
||
In practice, nobody, not even Git itself, runs <code class="literal">git cat-file</code> three times
|
||
for this. There is a <code class="literal">git merge-index</code> program that extracts the
|
||
stages to temporary files and calls a "merge" script on it:</p><pre class="screen">$ git merge-index git-merge-one-file hello.c</pre><p>and that is what higher level <code class="literal">git merge -s resolve</code> is implemented with.</p></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="hacking-git"></a>Part X. Hacking Git</h1></div></div></div><div class="partintro"><div></div><p>This chapter covers internal details of the Git implementation which
|
||
probably only Git developers need to understand.</p><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#object-details">55. Object storage format</a></span></dt><dt><span class="chapter"><a href="#birdview-on-the-source-code">56. A birds-eye view of Git’s source code</a></span></dt></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="object-details"></a>Chapter 55. Object storage format</h2></div></div></div><p>All objects have a statically determined "type" which identifies the
|
||
format of the object (i.e. how it is used, and how it can refer to other
|
||
objects). There are currently four different object types: "blob",
|
||
"tree", "commit", and "tag".</p><p>Regardless of object type, all objects share the following
|
||
characteristics: they are all deflated with zlib, and have a header
|
||
that not only specifies their type, but also provides size information
|
||
about the data in the object. It’s worth noting that the SHA-1 hash
|
||
that is used to name the object is the hash of the original data
|
||
plus this header, so <code class="literal">sha1sum</code> <span class="emphasis"><em>file</em></span> does not match the object name
|
||
for <span class="emphasis"><em>file</em></span>.</p><p>As a result, the general consistency of an object can always be tested
|
||
independently of the contents or the type of the object: all objects can
|
||
be validated by verifying that (a) their hashes match the content of the
|
||
file and (b) the object successfully inflates to a stream of bytes that
|
||
forms a sequence of
|
||
<code class="literal"><ascii type without space> + <space> + <ascii decimal size> +
|
||
<byte\0> + <binary object data></code>.</p><p>The structured objects can further have their structure and
|
||
connectivity to other objects verified. This is generally done with
|
||
the <code class="literal">git fsck</code> program, which generates a full dependency graph
|
||
of all objects, and verifies their internal consistency (in addition
|
||
to just verifying their superficial consistency through the hash).</p></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="birdview-on-the-source-code"></a>Chapter 56. A birds-eye view of Git’s source code</h2></div></div></div><p>It is not always easy for new developers to find their way through Git’s
|
||
source code. This section gives you a little guidance to show where to
|
||
start.</p><p>A good place to start is with the contents of the initial commit, with:</p><pre class="screen">$ git checkout e83c5163</pre><p>The initial revision lays the foundation for almost everything Git has
|
||
today, but is small enough to read in one sitting.</p><p>Note that terminology has changed since that revision. For example, the
|
||
README in that revision uses the word "changeset" to describe what we
|
||
now call a <a class="link" href="#def_commit_object">commit</a>.</p><p>Also, we do not call it "cache" any more, but rather "index"; however, the
|
||
file is still called <code class="literal">cache.h</code>. Remark: Not much reason to change it now,
|
||
especially since there is no good single name for it anyway, because it is
|
||
basically <span class="emphasis"><em>the</em></span> header file which is included by <span class="emphasis"><em>all</em></span> of Git’s C sources.</p><p>If you grasp the ideas in that initial commit, you should check out a
|
||
more recent version and skim <code class="literal">cache.h</code>, <code class="literal">object.h</code> and <code class="literal">commit.h</code>.</p><p>In the early days, Git (in the tradition of UNIX) was a bunch of programs
|
||
which were extremely simple, and which you used in scripts, piping the
|
||
output of one into another. This turned out to be good for initial
|
||
development, since it was easier to test new things. However, recently
|
||
many of these parts have become builtins, and some of the core has been
|
||
"libified", i.e. put into libgit.a for performance, portability reasons,
|
||
and to avoid code duplication.</p><p>By now, you know what the index is (and find the corresponding data
|
||
structures in <code class="literal">cache.h</code>), and that there are just a couple of object types
|
||
(blobs, trees, commits and tags) which inherit their common structure from
|
||
<code class="literal">struct object</code>, which is their first member (and thus, you can cast e.g.
|
||
<code class="literal">(struct object *)commit</code> to achieve the <span class="emphasis"><em>same</em></span> as <code class="literal">&commit->object</code>, i.e.
|
||
get at the object name and flags).</p><p>Now is a good point to take a break to let this information sink in.</p><p>Next step: get familiar with the object naming. Read <a class="xref" href="#naming-commits" title="Chapter 11. Naming commits">Chapter 11, <i>Naming commits</i></a>.
|
||
There are quite a few ways to name an object (and not only revisions!).
|
||
All of these are handled in <code class="literal">sha1_name.c</code>. Just have a quick look at
|
||
the function <code class="literal">get_sha1()</code>. A lot of the special handling is done by
|
||
functions like <code class="literal">get_sha1_basic()</code> or the likes.</p><p>This is just to get you into the groove for the most libified part of Git:
|
||
the revision walker.</p><p>Basically, the initial version of <code class="literal">git log</code> was a shell script:</p><pre class="screen">$ git-rev-list --pretty $(git-rev-parse --default HEAD "$@") | \
|
||
LESS=-S ${PAGER:-less}</pre><p>What does this mean?</p><p><code class="literal">git rev-list</code> is the original version of the revision walker, which
|
||
<span class="emphasis"><em>always</em></span> printed a list of revisions to stdout. It is still functional,
|
||
and needs to, since most new Git commands start out as scripts using
|
||
<code class="literal">git rev-list</code>.</p><p><code class="literal">git rev-parse</code> is not as important any more; it was only used to filter out
|
||
options that were relevant for the different plumbing commands that were
|
||
called by the script.</p><p>Most of what <code class="literal">git rev-list</code> did is contained in <code class="literal">revision.c</code> and
|
||
<code class="literal">revision.h</code>. It wraps the options in a struct named <code class="literal">rev_info</code>, which
|
||
controls how and what revisions are walked, and more.</p><p>The original job of <code class="literal">git rev-parse</code> is now taken by the function
|
||
<code class="literal">setup_revisions()</code>, which parses the revisions and the common command-line
|
||
options for the revision walker. This information is stored in the struct
|
||
<code class="literal">rev_info</code> for later consumption. You can do your own command-line option
|
||
parsing after calling <code class="literal">setup_revisions()</code>. After that, you have to call
|
||
<code class="literal">prepare_revision_walk()</code> for initialization, and then you can get the
|
||
commits one by one with the function <code class="literal">get_revision()</code>.</p><p>If you are interested in more details of the revision walking process,
|
||
just have a look at the first implementation of <code class="literal">cmd_log()</code>; call
|
||
<code class="literal">git show v1.3.0~155^2~4</code> and scroll down to that function (note that you
|
||
no longer need to call <code class="literal">setup_pager()</code> directly).</p><p>Nowadays, <code class="literal">git log</code> is a builtin, which means that it is <span class="emphasis"><em>contained</em></span> in the
|
||
command <code class="literal">git</code>. The source side of a builtin is</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">a function called <code class="literal">cmd_<bla></code>, typically defined in <code class="literal">builtin/<bla.c></code>
|
||
(note that older versions of Git used to have it in <code class="literal">builtin-<bla>.c</code>
|
||
instead), and declared in <code class="literal">builtin.h</code>.</li><li class="listitem">an entry in the <code class="literal">commands[]</code> array in <code class="literal">git.c</code>, and</li><li class="listitem">an entry in <code class="literal">BUILTIN_OBJECTS</code> in the <code class="literal">Makefile</code>.</li></ul></div><p>Sometimes, more than one builtin is contained in one source file. For
|
||
example, <code class="literal">cmd_whatchanged()</code> and <code class="literal">cmd_log()</code> both reside in <code class="literal">builtin/log.c</code>,
|
||
since they share quite a bit of code. In that case, the commands which are
|
||
<span class="emphasis"><em>not</em></span> named like the <code class="literal">.c</code> file in which they live have to be listed in
|
||
<code class="literal">BUILT_INS</code> in the <code class="literal">Makefile</code>.</p><p><code class="literal">git log</code> looks more complicated in C than it does in the original script,
|
||
but that allows for a much greater flexibility and performance.</p><p>Here again it is a good point to take a pause.</p><p>Lesson three is: study the code. Really, it is the best way to learn about
|
||
the organization of Git (after you know the basic concepts).</p><p>So, think about something which you are interested in, say, "how can I
|
||
access a blob just knowing the object name of it?". The first step is to
|
||
find a Git command with which you can do it. In this example, it is either
|
||
<code class="literal">git show</code> or <code class="literal">git cat-file</code>.</p><p>For the sake of clarity, let’s stay with <code class="literal">git cat-file</code>, because it</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">is plumbing, and</li><li class="listitem">was around even in the initial commit (it literally went only through
|
||
some 20 revisions as <code class="literal">cat-file.c</code>, was renamed to <code class="literal">builtin/cat-file.c</code>
|
||
when made a builtin, and then saw less than 10 versions).</li></ul></div><p>So, look into <code class="literal">builtin/cat-file.c</code>, search for <code class="literal">cmd_cat_file()</code> and look what
|
||
it does.</p><pre class="screen"> git_config(git_default_config);
|
||
if (argc != 3)
|
||
usage("git cat-file [-t|-s|-e|-p|<type>] <sha1>");
|
||
if (get_sha1(argv[2], sha1))
|
||
die("Not a valid object name %s", argv[2]);</pre><p>Let’s skip over the obvious details; the only really interesting part
|
||
here is the call to <code class="literal">get_sha1()</code>. It tries to interpret <code class="literal">argv[2]</code> as an
|
||
object name, and if it refers to an object which is present in the current
|
||
repository, it writes the resulting SHA-1 into the variable <code class="literal">sha1</code>.</p><p>Two things are interesting here:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><code class="literal">get_sha1()</code> returns 0 on <span class="emphasis"><em>success</em></span>. This might surprise some new
|
||
Git hackers, but there is a long tradition in UNIX to return different
|
||
negative numbers in case of different errors—and 0 on success.</li><li class="listitem">the variable <code class="literal">sha1</code> in the function signature of <code class="literal">get_sha1()</code> is <code class="literal">unsigned
|
||
char *</code>, but is actually expected to be a pointer to <code class="literal">unsigned
|
||
char[20]</code>. This variable will contain the 160-bit SHA-1 of the given
|
||
commit. Note that whenever a SHA-1 is passed as <code class="literal">unsigned char *</code>, it
|
||
is the binary representation, as opposed to the ASCII representation in
|
||
hex characters, which is passed as <code class="literal">char *</code>.</li></ul></div><p>You will see both of these things throughout the code.</p><p>Now, for the meat:</p><pre class="screen"> case 0:
|
||
buf = read_object_with_reference(sha1, argv[1], &size, NULL);</pre><p>This is how you read a blob (actually, not only a blob, but any type of
|
||
object). To know how the function <code class="literal">read_object_with_reference()</code> actually
|
||
works, find the source code for it (something like <code class="literal">git grep
|
||
read_object_with | grep ":[a-z]"</code> in the Git repository), and read
|
||
the source.</p><p>To find out how the result can be used, just read on in <code class="literal">cmd_cat_file()</code>:</p><pre class="screen"> write_or_die(1, buf, size);</pre><p>Sometimes, you do not know where to look for a feature. In many such cases,
|
||
it helps to search through the output of <code class="literal">git log</code>, and then <code class="literal">git show</code> the
|
||
corresponding commit.</p><p>Example: If you know that there was some test case for <code class="literal">git bundle</code>, but
|
||
do not remember where it was (yes, you <span class="emphasis"><em>could</em></span> <code class="literal">git grep bundle t/</code>, but that
|
||
does not illustrate the point!):</p><pre class="screen">$ git log --no-merges t/</pre><p>In the pager (<code class="literal">less</code>), just search for "bundle", go a few lines back,
|
||
and see that it is in commit 18449ab0. Now just copy this object name,
|
||
and paste it into the command line</p><pre class="screen">$ git show 18449ab0</pre><p>Voila.</p><p>Another example: Find out what to do in order to make some script a
|
||
builtin:</p><pre class="screen">$ git log --no-merges --diff-filter=A builtin/*.c</pre><p>You see, Git is actually the best tool to find out about the source of Git
|
||
itself!</p></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="glossary"></a>Part XI. Git Glossary</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#git-explained">57. Git explained</a></span></dt></dl></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="git-explained"></a>Chapter 57. Git explained</h2></div></div></div><div class="variablelist"><dl class="variablelist"><dt><span class="term"><a name="def_alternate_object_database"></a>alternate object database</span></dt><dd>Via the alternates mechanism, a <a class="link" href="#def_repository">repository</a>
|
||
can inherit part of its <a class="link" href="#def_object_database">object database</a>
|
||
from another object database, which is called an "alternate".</dd><dt><span class="term"><a name="def_bare_repository"></a>bare repository</span></dt><dd>A bare repository is normally an appropriately
|
||
named <a class="link" href="#def_directory">directory</a> with a <code class="literal">.git</code> suffix that does not
|
||
have a locally checked-out copy of any of the files under
|
||
revision control. That is, all of the Git
|
||
administrative and control files that would normally be present in the
|
||
hidden <code class="literal">.git</code> sub-directory are directly present in the
|
||
<code class="literal">repository.git</code> directory instead,
|
||
and no other files are present and checked out. Usually publishers of
|
||
public repositories make bare repositories available.</dd><dt><span class="term"><a name="def_blob_object"></a>blob object</span></dt><dd>Untyped <a class="link" href="#def_object">object</a>, e.g. the contents of a file.</dd><dt><span class="term"><a name="def_branch"></a>branch</span></dt><dd>A "branch" is an active line of development. The most recent
|
||
<a class="link" href="#def_commit">commit</a> on a branch is referred to as the tip of
|
||
that branch. The tip of the branch is referenced by a branch
|
||
<a class="link" href="#def_head">head</a>, which moves forward as additional development
|
||
is done on the branch. A single Git
|
||
<a class="link" href="#def_repository">repository</a> can track an arbitrary number of
|
||
branches, but your <a class="link" href="#def_working_tree">working tree</a> is
|
||
associated with just one of them (the "current" or "checked out"
|
||
branch), and <a class="link" href="#def_HEAD">HEAD</a> points to that branch.</dd><dt><span class="term"><a name="def_cache"></a>cache</span></dt><dd>Obsolete for: <a class="link" href="#def_index">index</a>.</dd><dt><span class="term"><a name="def_chain"></a>chain</span></dt><dd>A list of objects, where each <a class="link" href="#def_object">object</a> in the list contains
|
||
a reference to its successor (for example, the successor of a
|
||
<a class="link" href="#def_commit">commit</a> could be one of its <a class="link" href="#def_parent">parents</a>).</dd><dt><span class="term"><a name="def_changeset"></a>changeset</span></dt><dd>BitKeeper/cvsps speak for "<a class="link" href="#def_commit">commit</a>". Since Git does not
|
||
store changes, but states, it really does not make sense to use the term
|
||
"changesets" with Git.</dd><dt><span class="term"><a name="def_checkout"></a>checkout</span></dt><dd>The action of updating all or part of the
|
||
<a class="link" href="#def_working_tree">working tree</a> with a <a class="link" href="#def_tree_object">tree object</a>
|
||
or <a class="link" href="#def_blob_object">blob</a> from the
|
||
<a class="link" href="#def_object_database">object database</a>, and updating the
|
||
<a class="link" href="#def_index">index</a> and <a class="link" href="#def_HEAD">HEAD</a> if the whole working tree has
|
||
been pointed at a new <a class="link" href="#def_branch">branch</a>.</dd><dt><span class="term"><a name="def_cherry-picking"></a>cherry-picking</span></dt><dd>In <a class="link" href="#def_SCM">SCM</a> jargon, "cherry pick" means to choose a subset of
|
||
changes out of a series of changes (typically commits) and record them
|
||
as a new series of changes on top of a different codebase. In Git, this is
|
||
performed by the "git cherry-pick" command to extract the change introduced
|
||
by an existing <a class="link" href="#def_commit">commit</a> and to record it based on the tip
|
||
of the current <a class="link" href="#def_branch">branch</a> as a new commit.</dd><dt><span class="term"><a name="def_clean"></a>clean</span></dt><dd>A <a class="link" href="#def_working_tree">working tree</a> is clean, if it
|
||
corresponds to the <a class="link" href="#def_revision">revision</a> referenced by the current
|
||
<a class="link" href="#def_head">head</a>. Also see "<a class="link" href="#def_dirty">dirty</a>".</dd><dt><span class="term"><a name="def_commit"></a>commit</span></dt><dd><p class="simpara">As a noun: A single point in the
|
||
Git history; the entire history of a project is represented as a
|
||
set of interrelated commits. The word "commit" is often
|
||
used by Git in the same places other revision control systems
|
||
use the words "revision" or "version". Also used as a short
|
||
hand for <a class="link" href="#def_commit_object">commit object</a>.</p><p class="simpara">As a verb: The action of storing a new snapshot of the project’s
|
||
state in the Git history, by creating a new commit representing the current
|
||
state of the <a class="link" href="#def_index">index</a> and advancing <a class="link" href="#def_HEAD">HEAD</a>
|
||
to point at the new commit.</p></dd><dt><span class="term"><a name="def_commit_object"></a>commit object</span></dt><dd>An <a class="link" href="#def_object">object</a> which contains the information about a
|
||
particular <a class="link" href="#def_revision">revision</a>, such as <a class="link" href="#def_parent">parents</a>, committer,
|
||
author, date and the <a class="link" href="#def_tree_object">tree object</a> which corresponds
|
||
to the top <a class="link" href="#def_directory">directory</a> of the stored
|
||
revision.</dd><dt><span class="term"><a name="def_commit-ish"></a>commit-ish (also committish)</span></dt><dd>A <a class="link" href="#def_commit_object">commit object</a> or an
|
||
<a class="link" href="#def_object">object</a> that can be recursively dereferenced to
|
||
a commit object.
|
||
The following are all commit-ishes:
|
||
a commit object,
|
||
a <a class="link" href="#def_tag_object">tag object</a> that points to a commit
|
||
object,
|
||
a tag object that points to a tag object that points to a
|
||
commit object,
|
||
etc.</dd><dt><span class="term"><a name="def_core_git"></a>core Git</span></dt><dd>Fundamental data structures and utilities of Git. Exposes only limited
|
||
source code management tools.</dd><dt><span class="term"><a name="def_DAG"></a>DAG</span></dt><dd>Directed acyclic graph. The <a class="link" href="#def_commit_object">commit objects</a> form a
|
||
directed acyclic graph, because they have parents (directed), and the
|
||
graph of commit objects is acyclic (there is no <a class="link" href="#def_chain">chain</a>
|
||
which begins and ends with the same <a class="link" href="#def_object">object</a>).</dd><dt><span class="term"><a name="def_dangling_object"></a>dangling object</span></dt><dd>An <a class="link" href="#def_unreachable_object">unreachable object</a> which is not
|
||
<a class="link" href="#def_reachable">reachable</a> even from other unreachable objects; a
|
||
dangling object has no references to it from any
|
||
reference or <a class="link" href="#def_object">object</a> in the <a class="link" href="#def_repository">repository</a>.</dd><dt><span class="term"><a name="def_detached_HEAD"></a>detached HEAD</span></dt><dd><p class="simpara">Normally the <a class="link" href="#def_HEAD">HEAD</a> stores the name of a
|
||
<a class="link" href="#def_branch">branch</a>, and commands that operate on the
|
||
history HEAD represents operate on the history leading to the
|
||
tip of the branch the HEAD points at. However, Git also
|
||
allows you to <a class="link" href="#def_checkout">check out</a> an arbitrary
|
||
<a class="link" href="#def_commit">commit</a> that isn’t necessarily the tip of any
|
||
particular branch. The HEAD in such a state is called
|
||
"detached".</p><p class="simpara">Note that commands that operate on the history of the current branch
|
||
(e.g. <code class="literal">git commit</code> to build a new history on top of it) still work
|
||
while the HEAD is detached. They update the HEAD to point at the tip
|
||
of the updated history without affecting any branch. Commands that
|
||
update or inquire information <span class="emphasis"><em>about</em></span> the current branch (e.g. <code class="literal">git
|
||
branch --set-upstream-to</code> that sets what remote-tracking branch the
|
||
current branch integrates with) obviously do not work, as there is no
|
||
(real) current branch to ask about in this state.</p></dd><dt><span class="term"><a name="def_directory"></a>directory</span></dt><dd>The list you get with "ls" :-)</dd><dt><span class="term"><a name="def_dirty"></a>dirty</span></dt><dd>A <a class="link" href="#def_working_tree">working tree</a> is said to be "dirty" if
|
||
it contains modifications which have not been <a class="link" href="#def_commit">committed</a> to the current
|
||
<a class="link" href="#def_branch">branch</a>.</dd><dt><span class="term"><a name="def_evil_merge"></a>evil merge</span></dt><dd>An evil merge is a <a class="link" href="#def_merge">merge</a> that introduces changes that
|
||
do not appear in any <a class="link" href="#def_parent">parent</a>.</dd><dt><span class="term"><a name="def_fast_forward"></a>fast-forward</span></dt><dd>A fast-forward is a special type of <a class="link" href="#def_merge">merge</a> where you have a
|
||
<a class="link" href="#def_revision">revision</a> and you are "merging" another
|
||
<a class="link" href="#def_branch">branch</a>'s changes that happen to be a descendant of what
|
||
you have. In such a case, you do not make a new <a class="link" href="#def_merge">merge</a>
|
||
<a class="link" href="#def_commit">commit</a> but instead just update to his
|
||
revision. This will happen frequently on a
|
||
<a class="link" href="#def_remote_tracking_branch">remote-tracking branch</a> of a remote
|
||
<a class="link" href="#def_repository">repository</a>.</dd><dt><span class="term"><a name="def_fetch"></a>fetch</span></dt><dd>Fetching a <a class="link" href="#def_branch">branch</a> means to get the
|
||
branch’s <a class="link" href="#def_head_ref">head ref</a> from a remote
|
||
<a class="link" href="#def_repository">repository</a>, to find out which objects are
|
||
missing from the local <a class="link" href="#def_object_database">object database</a>,
|
||
and to get them, too. See also git-fetch(1).</dd><dt><span class="term"><a name="def_file_system"></a>file system</span></dt><dd>Linus Torvalds originally designed Git to be a user space file system,
|
||
i.e. the infrastructure to hold files and directories. That ensured the
|
||
efficiency and speed of Git.</dd><dt><span class="term"><a name="def_git_archive"></a>Git archive</span></dt><dd>Synonym for <a class="link" href="#def_repository">repository</a> (for arch people).</dd><dt><span class="term"><a name="def_gitfile"></a>gitfile</span></dt><dd>A plain file <code class="literal">.git</code> at the root of a working tree that
|
||
points at the directory that is the real repository.</dd><dt><span class="term"><a name="def_grafts"></a>grafts</span></dt><dd><p class="simpara">Grafts enables two otherwise different lines of development to be joined
|
||
together by recording fake ancestry information for commits. This way
|
||
you can make Git pretend the set of <a class="link" href="#def_parent">parents</a> a <a class="link" href="#def_commit">commit</a> has
|
||
is different from what was recorded when the commit was
|
||
created. Configured via the <code class="literal">.git/info/grafts</code> file.</p><p class="simpara">Note that the grafts mechanism is outdated and can lead to problems
|
||
transferring objects between repositories; see git-replace(1)
|
||
for a more flexible and robust system to do the same thing.</p></dd><dt><span class="term"><a name="def_hash"></a>hash</span></dt><dd>In Git’s context, synonym for <a class="link" href="#def_object_name">object name</a>.</dd><dt><span class="term"><a name="def_head"></a>head</span></dt><dd>A <a class="link" href="#def_ref">named reference</a> to the <a class="link" href="#def_commit">commit</a> at the tip of a
|
||
<a class="link" href="#def_branch">branch</a>. Heads are stored in a file in
|
||
<code class="literal">$GIT_DIR/refs/heads/</code> directory, except when using packed refs. (See
|
||
git-pack-refs(1).)</dd><dt><span class="term"><a name="def_HEAD"></a>HEAD</span></dt><dd>The current <a class="link" href="#def_branch">branch</a>. In more detail: Your <a class="link" href="#def_working_tree">working tree</a> is normally derived from the state of the tree
|
||
referred to by HEAD. HEAD is a reference to one of the
|
||
<a class="link" href="#def_head">heads</a> in your repository, except when using a
|
||
<a class="link" href="#def_detached_HEAD">detached HEAD</a>, in which case it directly
|
||
references an arbitrary commit.</dd><dt><span class="term"><a name="def_head_ref"></a>head ref</span></dt><dd>A synonym for <a class="link" href="#def_head">head</a>.</dd><dt><span class="term"><a name="def_hook"></a>hook</span></dt><dd>During the normal execution of several Git commands, call-outs are made
|
||
to optional scripts that allow a developer to add functionality or
|
||
checking. Typically, the hooks allow for a command to be pre-verified
|
||
and potentially aborted, and allow for a post-notification after the
|
||
operation is done. The hook scripts are found in the
|
||
<code class="literal">$GIT_DIR/hooks/</code> directory, and are enabled by simply
|
||
removing the <code class="literal">.sample</code> suffix from the filename. In earlier versions
|
||
of Git you had to make them executable.</dd><dt><span class="term"><a name="def_index"></a>index</span></dt><dd>A collection of files with stat information, whose contents are stored
|
||
as objects. The index is a stored version of your
|
||
<a class="link" href="#def_working_tree">working tree</a>. Truth be told, it can also contain a second, and even
|
||
a third version of a working tree, which are used
|
||
when <a class="link" href="#def_merge">merging</a>.</dd><dt><span class="term"><a name="def_index_entry"></a>index entry</span></dt><dd>The information regarding a particular file, stored in the
|
||
<a class="link" href="#def_index">index</a>. An index entry can be unmerged, if a
|
||
<a class="link" href="#def_merge">merge</a> was started, but not yet finished (i.e. if
|
||
the index contains multiple versions of that file).</dd><dt><span class="term"><a name="def_master"></a>master</span></dt><dd>The default development <a class="link" href="#def_branch">branch</a>. Whenever you
|
||
create a Git <a class="link" href="#def_repository">repository</a>, a branch named
|
||
"master" is created, and becomes the active branch. In most
|
||
cases, this contains the local development, though that is
|
||
purely by convention and is not required.</dd><dt><span class="term"><a name="def_merge"></a>merge</span></dt><dd><p class="simpara">As a verb: To bring the contents of another
|
||
<a class="link" href="#def_branch">branch</a> (possibly from an external
|
||
<a class="link" href="#def_repository">repository</a>) into the current branch. In the
|
||
case where the merged-in branch is from a different repository,
|
||
this is done by first <a class="link" href="#def_fetch">fetching</a> the remote branch
|
||
and then merging the result into the current branch. This
|
||
combination of fetch and merge operations is called a
|
||
<a class="link" href="#def_pull">pull</a>. Merging is performed by an automatic process
|
||
that identifies changes made since the branches diverged, and
|
||
then applies all those changes together. In cases where changes
|
||
conflict, manual intervention may be required to complete the
|
||
merge.</p><p class="simpara">As a noun: unless it is a <a class="link" href="#def_fast_forward">fast-forward</a>, a
|
||
successful merge results in the creation of a new <a class="link" href="#def_commit">commit</a>
|
||
representing the result of the merge, and having as
|
||
<a class="link" href="#def_parent">parents</a> the tips of the merged <a class="link" href="#def_branch">branches</a>.
|
||
This commit is referred to as a "merge commit", or sometimes just a
|
||
"merge".</p></dd><dt><span class="term"><a name="def_object"></a>object</span></dt><dd>The unit of storage in Git. It is uniquely identified by the
|
||
<a class="link" href="#def_SHA1">SHA-1</a> of its contents. Consequently, an
|
||
object can not be changed.</dd><dt><span class="term"><a name="def_object_database"></a>object database</span></dt><dd>Stores a set of "objects", and an individual <a class="link" href="#def_object">object</a> is
|
||
identified by its <a class="link" href="#def_object_name">object name</a>. The objects usually
|
||
live in <code class="literal">$GIT_DIR/objects/</code>.</dd><dt><span class="term"><a name="def_object_identifier"></a>object identifier</span></dt><dd>Synonym for <a class="link" href="#def_object_name">object name</a>.</dd><dt><span class="term"><a name="def_object_name"></a>object name</span></dt><dd>The unique identifier of an <a class="link" href="#def_object">object</a>. The
|
||
object name is usually represented by a 40 character
|
||
hexadecimal string. Also colloquially called <a class="link" href="#def_SHA1">SHA-1</a>.</dd><dt><span class="term"><a name="def_object_type"></a>object type</span></dt><dd>One of the identifiers "<a class="link" href="#def_commit_object">commit</a>",
|
||
"<a class="link" href="#def_tree_object">tree</a>", "<a class="link" href="#def_tag_object">tag</a>" or
|
||
"<a class="link" href="#def_blob_object">blob</a>" describing the type of an
|
||
<a class="link" href="#def_object">object</a>.</dd><dt><span class="term"><a name="def_octopus"></a>octopus</span></dt><dd>To <a class="link" href="#def_merge">merge</a> more than two <a class="link" href="#def_branch">branches</a>.</dd><dt><span class="term"><a name="def_origin"></a>origin</span></dt><dd>The default upstream <a class="link" href="#def_repository">repository</a>. Most projects have
|
||
at least one upstream project which they track. By default
|
||
<span class="emphasis"><em>origin</em></span> is used for that purpose. New upstream updates
|
||
will be fetched into <a class="link" href="#def_remote_tracking_branch">remote-tracking branches</a> named
|
||
origin/name-of-upstream-branch, which you can see using
|
||
<code class="literal">git branch -r</code>.</dd><dt><span class="term"><a name="def_pack"></a>pack</span></dt><dd>A set of objects which have been compressed into one file (to save space
|
||
or to transmit them efficiently).</dd><dt><span class="term"><a name="def_pack_index"></a>pack index</span></dt><dd>The list of identifiers, and other information, of the objects in a
|
||
<a class="link" href="#def_pack">pack</a>, to assist in efficiently accessing the contents of a
|
||
pack.</dd><dt><span class="term"><a name="def_pathspec"></a>pathspec</span></dt><dd><p class="simpara">Pattern used to limit paths in Git commands.</p><p class="simpara">Pathspecs are used on the command line of "git ls-files", "git
|
||
ls-tree", "git add", "git grep", "git diff", "git checkout",
|
||
and many other commands to
|
||
limit the scope of operations to some subset of the tree or
|
||
worktree. See the documentation of each command for whether
|
||
paths are relative to the current directory or toplevel. The
|
||
pathspec syntax is as follows:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">any path matches itself</li><li class="listitem">the pathspec up to the last slash represents a
|
||
directory prefix. The scope of that pathspec is
|
||
limited to that subtree.</li><li class="listitem">the rest of the pathspec is a pattern for the remainder
|
||
of the pathname. Paths relative to the directory
|
||
prefix will be matched against that pattern using fnmatch(3);
|
||
in particular, <span class="emphasis"><em>*</em></span> and <span class="emphasis"><em>?</em></span> <span class="emphasis"><em>can</em></span> match directory separators.</li></ul></div><p class="simpara">For example, Documentation/*.jpg will match all .jpg files
|
||
in the Documentation subtree,
|
||
including Documentation/chapter_1/figure_1.jpg.</p><p class="simpara">A pathspec that begins with a colon <code class="literal">:</code> has special meaning. In the
|
||
short form, the leading colon <code class="literal">:</code> is followed by zero or more "magic
|
||
signature" letters (which optionally is terminated by another colon <code class="literal">:</code>),
|
||
and the remainder is the pattern to match against the path.
|
||
The "magic signature" consists of ASCII symbols that are neither
|
||
alphanumeric, glob, regex special characters nor colon.
|
||
The optional colon that terminates the "magic signature" can be
|
||
omitted if the pattern begins with a character that does not belong to
|
||
"magic signature" symbol set and is not a colon.</p><p class="simpara">In the long form, the leading colon <code class="literal">:</code> is followed by an open
|
||
parenthesis <code class="literal">(</code>, a comma-separated list of zero or more "magic words",
|
||
and a close parentheses <code class="literal">)</code>, and the remainder is the pattern to match
|
||
against the path.</p><p class="simpara">A pathspec with only a colon means "there is no pathspec". This form
|
||
should not be combined with other pathspec.</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">top</span></dt><dd>The magic word <code class="literal">top</code> (magic signature: <code class="literal">/</code>) makes the pattern
|
||
match from the root of the working tree, even when you are
|
||
running the command from inside a subdirectory.</dd><dt><span class="term">literal</span></dt><dd>Wildcards in the pattern such as <code class="literal">*</code> or <code class="literal">?</code> are treated
|
||
as literal characters.</dd><dt><span class="term">icase</span></dt><dd>Case insensitive match.</dd><dt><span class="term">glob</span></dt><dd><p class="simpara">Git treats the pattern as a shell glob suitable for
|
||
consumption by fnmatch(3) with the FNM_PATHNAME flag:
|
||
wildcards in the pattern will not match a / in the pathname.
|
||
For example, "Documentation/*.html" matches
|
||
"Documentation/git.html" but not "Documentation/ppc/ppc.html"
|
||
or "tools/perf/Documentation/perf.html".</p><p class="simpara">Two consecutive asterisks ("<code class="literal">**</code>") in patterns matched against
|
||
full pathname may have special meaning:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">A leading "<code class="literal">**</code>" followed by a slash means match in all
|
||
directories. For example, "<code class="literal">**/foo</code>" matches file or directory
|
||
"<code class="literal">foo</code>" anywhere, the same as pattern "<code class="literal">foo</code>". "<code class="literal">**/foo/bar</code>"
|
||
matches file or directory "<code class="literal">bar</code>" anywhere that is directly
|
||
under directory "<code class="literal">foo</code>".</li><li class="listitem">A trailing "<code class="literal">/**</code>" matches everything inside. For example,
|
||
"<code class="literal">abc/**</code>" matches all files inside directory "abc", relative
|
||
to the location of the <code class="literal">.gitignore</code> file, with infinite depth.</li><li class="listitem">A slash followed by two consecutive asterisks then a slash
|
||
matches zero or more directories. For example, "<code class="literal">a/**/b</code>"
|
||
matches "<code class="literal">a/b</code>", "<code class="literal">a/x/b</code>", "<code class="literal">a/x/y/b</code>" and so on.</li><li class="listitem"><p class="simpara">Other consecutive asterisks are considered invalid.</p><p class="simpara">Glob magic is incompatible with literal magic.</p></li></ul></div></dd><dt><span class="term">attr</span></dt><dd><p class="simpara">After <code class="literal">attr:</code> comes a space separated list of "attribute
|
||
requirements", all of which must be met in order for the
|
||
path to be considered a match; this is in addition to the
|
||
usual non-magic pathspec pattern matching.
|
||
See gitattributes(5).</p><p class="simpara">Each of the attribute requirements for the path takes one of
|
||
these forms:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">"<code class="literal">ATTR</code>" requires that the attribute <code class="literal">ATTR</code> be set.</li><li class="listitem">"<code class="literal">-ATTR</code>" requires that the attribute <code class="literal">ATTR</code> be unset.</li><li class="listitem">"<code class="literal">ATTR=VALUE</code>" requires that the attribute <code class="literal">ATTR</code> be
|
||
set to the string <code class="literal">VALUE</code>.</li><li class="listitem"><p class="simpara">"<code class="literal">!ATTR</code>" requires that the attribute <code class="literal">ATTR</code> be
|
||
unspecified.</p><p class="simpara">Note that when matching against a tree object, attributes are still
|
||
obtained from working tree, not from the given tree object.</p></li></ul></div></dd><dt><span class="term">exclude</span></dt><dd>After a path matches any non-exclude pathspec, it will be run
|
||
through all exclude pathspecs (magic signature: <code class="literal">!</code> or its
|
||
synonym <code class="literal">^</code>). If it matches, the path is ignored. When there
|
||
is no non-exclude pathspec, the exclusion is applied to the
|
||
result set as if invoked without any pathspec.</dd></dl></div></dd><dt><span class="term"><a name="def_parent"></a>parent</span></dt><dd>A <a class="link" href="#def_commit_object">commit object</a> contains a (possibly empty) list
|
||
of the logical predecessor(s) in the line of development, i.e. its
|
||
parents.</dd><dt><span class="term"><a name="def_pickaxe"></a>pickaxe</span></dt><dd>The term <a class="link" href="#def_pickaxe">pickaxe</a> refers to an option to the diffcore
|
||
routines that help select changes that add or delete a given text
|
||
string. With the <code class="literal">--pickaxe-all</code> option, it can be used to view the full
|
||
<a class="link" href="#def_changeset">changeset</a> that introduced or removed, say, a
|
||
particular line of text. See git-diff(1).</dd><dt><span class="term"><a name="def_plumbing"></a>plumbing</span></dt><dd>Cute name for <a class="link" href="#def_core_git">core Git</a>.</dd><dt><span class="term"><a name="def_porcelain"></a>porcelain</span></dt><dd>Cute name for programs and program suites depending on
|
||
<a class="link" href="#def_core_git">core Git</a>, presenting a high level access to
|
||
core Git. Porcelains expose more of a <a class="link" href="#def_SCM">SCM</a>
|
||
interface than the <a class="link" href="#def_plumbing">plumbing</a>.</dd><dt><span class="term"><a name="def_per_worktree_ref"></a>per-worktree ref</span></dt><dd>Refs that are per-<a class="link" href="#def_working_tree">worktree</a>, rather than
|
||
global. This is presently only <a class="link" href="#def_HEAD">HEAD</a> and any refs
|
||
that start with <code class="literal">refs/bisect/</code>, but might later include other
|
||
unusual refs.</dd><dt><span class="term"><a name="def_pseudoref"></a>pseudoref</span></dt><dd>Pseudorefs are a class of files under <code class="literal">$GIT_DIR</code> which behave
|
||
like refs for the purposes of rev-parse, but which are treated
|
||
specially by git. Pseudorefs both have names that are all-caps,
|
||
and always start with a line consisting of a
|
||
<a class="link" href="#def_SHA1">SHA-1</a> followed by whitespace. So, HEAD is not a
|
||
pseudoref, because it is sometimes a symbolic ref. They might
|
||
optionally contain some additional data. <code class="literal">MERGE_HEAD</code> and
|
||
<code class="literal">CHERRY_PICK_HEAD</code> are examples. Unlike
|
||
<a class="link" href="#def_per_worktree_ref">per-worktree refs</a>, these files cannot
|
||
be symbolic refs, and never have reflogs. They also cannot be
|
||
updated through the normal ref update machinery. Instead,
|
||
they are updated by directly writing to the files. However,
|
||
they can be read as if they were refs, so <code class="literal">git rev-parse
|
||
MERGE_HEAD</code> will work.</dd><dt><span class="term"><a name="def_pull"></a>pull</span></dt><dd>Pulling a <a class="link" href="#def_branch">branch</a> means to <a class="link" href="#def_fetch">fetch</a> it and
|
||
<a class="link" href="#def_merge">merge</a> it. See also git-pull(1).</dd><dt><span class="term"><a name="def_push"></a>push</span></dt><dd>Pushing a <a class="link" href="#def_branch">branch</a> means to get the branch’s
|
||
<a class="link" href="#def_head_ref">head ref</a> from a remote <a class="link" href="#def_repository">repository</a>,
|
||
find out if it is an ancestor to the branch’s local
|
||
head ref, and in that case, putting all
|
||
objects, which are <a class="link" href="#def_reachable">reachable</a> from the local
|
||
head ref, and which are missing from the remote
|
||
repository, into the remote
|
||
<a class="link" href="#def_object_database">object database</a>, and updating the remote
|
||
head ref. If the remote <a class="link" href="#def_head">head</a> is not an
|
||
ancestor to the local head, the push fails.</dd><dt><span class="term"><a name="def_reachable"></a>reachable</span></dt><dd>All of the ancestors of a given <a class="link" href="#def_commit">commit</a> are said to be
|
||
"reachable" from that commit. More
|
||
generally, one <a class="link" href="#def_object">object</a> is reachable from
|
||
another if we can reach the one from the other by a <a class="link" href="#def_chain">chain</a>
|
||
that follows <a class="link" href="#def_tag">tags</a> to whatever they tag,
|
||
<a class="link" href="#def_commit_object">commits</a> to their parents or trees, and
|
||
<a class="link" href="#def_tree_object">trees</a> to the trees or <a class="link" href="#def_blob_object">blobs</a>
|
||
that they contain.</dd><dt><span class="term"><a name="def_rebase"></a>rebase</span></dt><dd>To reapply a series of changes from a <a class="link" href="#def_branch">branch</a> to a
|
||
different base, and reset the <a class="link" href="#def_head">head</a> of that branch
|
||
to the result.</dd><dt><span class="term"><a name="def_ref"></a>ref</span></dt><dd><p class="simpara">A name that begins with <code class="literal">refs/</code> (e.g. <code class="literal">refs/heads/master</code>)
|
||
that points to an <a class="link" href="#def_object_name">object name</a> or another
|
||
ref (the latter is called a <a class="link" href="#def_symref">symbolic ref</a>).
|
||
For convenience, a ref can sometimes be abbreviated when used
|
||
as an argument to a Git command; see gitrevisions(7)
|
||
for details.
|
||
Refs are stored in the <a class="link" href="#def_repository">repository</a>.</p><p class="simpara">The ref namespace is hierarchical.
|
||
Different subhierarchies are used for different purposes (e.g. the
|
||
<code class="literal">refs/heads/</code> hierarchy is used to represent local branches).</p><p class="simpara">There are a few special-purpose refs that do not begin with <code class="literal">refs/</code>.
|
||
The most notable example is <code class="literal">HEAD</code>.</p></dd><dt><span class="term"><a name="def_reflog"></a>reflog</span></dt><dd>A reflog shows the local "history" of a ref. In other words,
|
||
it can tell you what the 3rd last revision in <span class="emphasis"><em>this</em></span> repository
|
||
was, and what was the current state in <span class="emphasis"><em>this</em></span> repository,
|
||
yesterday 9:14pm. See git-reflog(1) for details.</dd><dt><span class="term"><a name="def_refspec"></a>refspec</span></dt><dd>A "refspec" is used by <a class="link" href="#def_fetch">fetch</a> and
|
||
<a class="link" href="#def_push">push</a> to describe the mapping between remote
|
||
<a class="link" href="#def_ref">ref</a> and local ref.</dd><dt><span class="term"><a name="def_remote"></a>remote repository</span></dt><dd>A <a class="link" href="#def_repository">repository</a> which is used to track the same
|
||
project but resides somewhere else. To communicate with remotes,
|
||
see <a class="link" href="#def_fetch">fetch</a> or <a class="link" href="#def_push">push</a>.</dd><dt><span class="term"><a name="def_remote_tracking_branch"></a>remote-tracking branch</span></dt><dd>A <a class="link" href="#def_ref">ref</a> that is used to follow changes from another
|
||
<a class="link" href="#def_repository">repository</a>. It typically looks like
|
||
<span class="emphasis"><em>refs/remotes/foo/bar</em></span> (indicating that it tracks a branch named
|
||
<span class="emphasis"><em>bar</em></span> in a remote named <span class="emphasis"><em>foo</em></span>), and matches the right-hand-side of
|
||
a configured fetch <a class="link" href="#def_refspec">refspec</a>. A remote-tracking
|
||
branch should not contain direct modifications or have local
|
||
commits made to it.</dd><dt><span class="term"><a name="def_repository"></a>repository</span></dt><dd>A collection of <a class="link" href="#def_ref">refs</a> together with an
|
||
<a class="link" href="#def_object_database">object database</a> containing all objects
|
||
which are <a class="link" href="#def_reachable">reachable</a> from the refs, possibly
|
||
accompanied by meta data from one or more <a class="link" href="#def_porcelain">porcelains</a>. A
|
||
repository can share an object database with other repositories
|
||
via <a class="link" href="#def_alternate_object_database">alternates mechanism</a>.</dd><dt><span class="term"><a name="def_resolve"></a>resolve</span></dt><dd>The action of fixing up manually what a failed automatic
|
||
<a class="link" href="#def_merge">merge</a> left behind.</dd><dt><span class="term"><a name="def_revision"></a>revision</span></dt><dd>Synonym for <a class="link" href="#def_commit">commit</a> (the noun).</dd><dt><span class="term"><a name="def_rewind"></a>rewind</span></dt><dd>To throw away part of the development, i.e. to assign the
|
||
<a class="link" href="#def_head">head</a> to an earlier <a class="link" href="#def_revision">revision</a>.</dd><dt><span class="term"><a name="def_SCM"></a>SCM</span></dt><dd>Source code management (tool).</dd><dt><span class="term"><a name="def_SHA1"></a>SHA-1</span></dt><dd>"Secure Hash Algorithm 1"; a cryptographic hash function.
|
||
In the context of Git used as a synonym for <a class="link" href="#def_object_name">object name</a>.</dd><dt><span class="term"><a name="def_shallow_clone"></a>shallow clone</span></dt><dd>Mostly a synonym to <a class="link" href="#def_shallow_repository">shallow repository</a>
|
||
but the phrase makes it more explicit that it was created by
|
||
running <code class="literal">git clone --depth=...</code> command.</dd><dt><span class="term"><a name="def_shallow_repository"></a>shallow repository</span></dt><dd>A shallow <a class="link" href="#def_repository">repository</a> has an incomplete
|
||
history some of whose <a class="link" href="#def_commit">commits</a> have <a class="link" href="#def_parent">parents</a> cauterized away (in other
|
||
words, Git is told to pretend that these commits do not have the
|
||
parents, even though they are recorded in the <a class="link" href="#def_commit_object">commit
|
||
object</a>). This is sometimes useful when you are interested only in the
|
||
recent history of a project even though the real history recorded in the
|
||
upstream is much larger. A shallow repository
|
||
is created by giving the <code class="literal">--depth</code> option to git-clone(1), and
|
||
its history can be later deepened with git-fetch(1).</dd><dt><span class="term"><a name="def_stash"></a>stash entry</span></dt><dd>An <a class="link" href="#def_object">object</a> used to temporarily store the contents of a
|
||
<a class="link" href="#def_dirty">dirty</a> working directory and the index for future reuse.</dd><dt><span class="term"><a name="def_submodule"></a>submodule</span></dt><dd>A <a class="link" href="#def_repository">repository</a> that holds the history of a
|
||
separate project inside another repository (the latter of
|
||
which is called <a class="link" href="#def_superproject">superproject</a>).</dd><dt><span class="term"><a name="def_superproject"></a>superproject</span></dt><dd>A <a class="link" href="#def_repository">repository</a> that references repositories
|
||
of other projects in its working tree as <a class="link" href="#def_submodule">submodules</a>.
|
||
The superproject knows about the names of (but does not hold
|
||
copies of) commit objects of the contained submodules.</dd><dt><span class="term"><a name="def_symref"></a>symref</span></dt><dd>Symbolic reference: instead of containing the <a class="link" href="#def_SHA1">SHA-1</a>
|
||
id itself, it is of the format <span class="emphasis"><em>ref: refs/some/thing</em></span> and when
|
||
referenced, it recursively dereferences to this reference.
|
||
<span class="emphasis"><em><a class="link" href="#def_HEAD">HEAD</a></em></span> is a prime example of a symref. Symbolic
|
||
references are manipulated with the git-symbolic-ref(1)
|
||
command.</dd><dt><span class="term"><a name="def_tag"></a>tag</span></dt><dd>A <a class="link" href="#def_ref">ref</a> under <code class="literal">refs/tags/</code> namespace that points to an
|
||
object of an arbitrary type (typically a tag points to either a
|
||
<a class="link" href="#def_tag_object">tag</a> or a <a class="link" href="#def_commit_object">commit object</a>).
|
||
In contrast to a <a class="link" href="#def_head">head</a>, a tag is not updated by
|
||
the <code class="literal">commit</code> command. A Git tag has nothing to do with a Lisp
|
||
tag (which would be called an <a class="link" href="#def_object_type">object type</a>
|
||
in Git’s context). A tag is most typically used to mark a particular
|
||
point in the commit ancestry <a class="link" href="#def_chain">chain</a>.</dd><dt><span class="term"><a name="def_tag_object"></a>tag object</span></dt><dd>An <a class="link" href="#def_object">object</a> containing a <a class="link" href="#def_ref">ref</a> pointing to
|
||
another object, which can contain a message just like a
|
||
<a class="link" href="#def_commit_object">commit object</a>. It can also contain a (PGP)
|
||
signature, in which case it is called a "signed tag object".</dd><dt><span class="term"><a name="def_topic_branch"></a>topic branch</span></dt><dd>A regular Git <a class="link" href="#def_branch">branch</a> that is used by a developer to
|
||
identify a conceptual line of development. Since branches are very easy
|
||
and inexpensive, it is often desirable to have several small branches
|
||
that each contain very well defined concepts or small incremental yet
|
||
related changes.</dd><dt><span class="term"><a name="def_tree"></a>tree</span></dt><dd>Either a <a class="link" href="#def_working_tree">working tree</a>, or a <a class="link" href="#def_tree_object">tree
|
||
object</a> together with the dependent <a class="link" href="#def_blob_object">blob</a> and tree objects
|
||
(i.e. a stored representation of a working tree).</dd><dt><span class="term"><a name="def_tree_object"></a>tree object</span></dt><dd>An <a class="link" href="#def_object">object</a> containing a list of file names and modes along
|
||
with refs to the associated blob and/or tree objects. A
|
||
<a class="link" href="#def_tree">tree</a> is equivalent to a <a class="link" href="#def_directory">directory</a>.</dd><dt><span class="term"><a name="def_tree-ish"></a>tree-ish (also treeish)</span></dt><dd>A <a class="link" href="#def_tree_object">tree object</a> or an <a class="link" href="#def_object">object</a>
|
||
that can be recursively dereferenced to a tree object.
|
||
Dereferencing a <a class="link" href="#def_commit_object">commit object</a> yields the
|
||
tree object corresponding to the <a class="link" href="#def_revision">revision</a>'s
|
||
top <a class="link" href="#def_directory">directory</a>.
|
||
The following are all tree-ishes:
|
||
a <a class="link" href="#def_commit-ish">commit-ish</a>,
|
||
a tree object,
|
||
a <a class="link" href="#def_tag_object">tag object</a> that points to a tree object,
|
||
a tag object that points to a tag object that points to a tree
|
||
object,
|
||
etc.</dd><dt><span class="term"><a name="def_unmerged_index"></a>unmerged index</span></dt><dd>An <a class="link" href="#def_index">index</a> which contains unmerged
|
||
<a class="link" href="#def_index_entry">index entries</a>.</dd><dt><span class="term"><a name="def_unreachable_object"></a>unreachable object</span></dt><dd>An <a class="link" href="#def_object">object</a> which is not <a class="link" href="#def_reachable">reachable</a> from a
|
||
<a class="link" href="#def_branch">branch</a>, <a class="link" href="#def_tag">tag</a>, or any other reference.</dd><dt><span class="term"><a name="def_upstream_branch"></a>upstream branch</span></dt><dd>The default <a class="link" href="#def_branch">branch</a> that is merged into the branch in
|
||
question (or the branch in question is rebased onto). It is configured
|
||
via branch.<name>.remote and branch.<name>.merge. If the upstream branch
|
||
of <span class="emphasis"><em>A</em></span> is <span class="emphasis"><em>origin/B</em></span> sometimes we say "<span class="emphasis"><em>A</em></span> is tracking <span class="emphasis"><em>origin/B</em></span>".</dd><dt><span class="term"><a name="def_working_tree"></a>working tree</span></dt><dd>The tree of actual checked out files. The working tree normally
|
||
contains the contents of the <a class="link" href="#def_HEAD">HEAD</a> commit’s tree,
|
||
plus any local changes that you have made but not yet committed.</dd></dl></div></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="git-quick-start"></a>Part XII. Appendix A: Git Quick Reference</h1></div></div></div><div class="partintro"><div></div><p>This is a quick summary of the major commands; the previous chapters
|
||
explain how these work in more detail.</p><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#quick-creating-a-new-repository">58. Creating a new repository</a></span></dt><dt><span class="chapter"><a href="#managing-branches">59. Managing branches</a></span></dt><dt><span class="chapter"><a href="#exploring-history">60. Exploring history</a></span></dt><dt><span class="chapter"><a href="#making-changes">61. Making changes</a></span></dt><dt><span class="chapter"><a href="#merging">62. Merging</a></span></dt><dt><span class="chapter"><a href="#sharing-your-changes">63. Sharing your changes</a></span></dt><dt><span class="chapter"><a href="#repository-maintenance">64. Repository maintenance</a></span></dt></dl></div></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="quick-creating-a-new-repository"></a>Chapter 58. Creating a new repository</h2></div></div></div><p>From a tarball:</p><pre class="screen">$ tar xzf project.tar.gz
|
||
$ cd project
|
||
$ git init
|
||
Initialized empty Git repository in .git/
|
||
$ git add .
|
||
$ git commit</pre><p>From a remote repository:</p><pre class="screen">$ git clone git://example.com/pub/project.git
|
||
$ cd project</pre></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="managing-branches"></a>Chapter 59. Managing branches</h2></div></div></div><pre class="screen">$ git branch # list all local branches in this repo
|
||
$ git checkout test # switch working directory to branch "test"
|
||
$ git branch new # create branch "new" starting at current HEAD
|
||
$ git branch -d new # delete branch "new"</pre><p>Instead of basing a new branch on current HEAD (the default), use:</p><pre class="screen">$ git branch new test # branch named "test"
|
||
$ git branch new v2.6.15 # tag named v2.6.15
|
||
$ git branch new HEAD^ # commit before the most recent
|
||
$ git branch new HEAD^^ # commit before that
|
||
$ git branch new test~10 # ten commits before tip of branch "test"</pre><p>Create and switch to a new branch at the same time:</p><pre class="screen">$ git checkout -b new v2.6.15</pre><p>Update and examine branches from the repository you cloned from:</p><pre class="screen">$ git fetch # update
|
||
$ git branch -r # list
|
||
origin/master
|
||
origin/next
|
||
...
|
||
$ git checkout -b masterwork origin/master</pre><p>Fetch a branch from a different repository, and give it a new
|
||
name in your repository:</p><pre class="screen">$ git fetch git://example.com/project.git theirbranch:mybranch
|
||
$ git fetch git://example.com/project.git v2.6.15:mybranch</pre><p>Keep a list of repositories you work with regularly:</p><pre class="screen">$ git remote add example git://example.com/project.git
|
||
$ git remote # list remote repositories
|
||
example
|
||
origin
|
||
$ git remote show example # get details
|
||
* remote example
|
||
URL: git://example.com/project.git
|
||
Tracked remote branches
|
||
master
|
||
next
|
||
...
|
||
$ git fetch example # update branches from example
|
||
$ git branch -r # list all remote branches</pre></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="exploring-history"></a>Chapter 60. Exploring history</h2></div></div></div><pre class="screen">$ gitk # visualize and browse history
|
||
$ git log # list all commits
|
||
$ git log src/ # ...modifying src/
|
||
$ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15
|
||
$ git log master..test # ...in branch test, not in branch master
|
||
$ git log test..master # ...in branch master, but not in test
|
||
$ git log test...master # ...in one branch, not in both
|
||
$ git log -S'foo()' # ...where difference contain "foo()"
|
||
$ git log --since="2 weeks ago"
|
||
$ git log -p # show patches as well
|
||
$ git show # most recent commit
|
||
$ git diff v2.6.15..v2.6.16 # diff between two tagged versions
|
||
$ git diff v2.6.15..HEAD # diff with current head
|
||
$ git grep "foo()" # search working directory for "foo()"
|
||
$ git grep v2.6.15 "foo()" # search old tree for "foo()"
|
||
$ git show v2.6.15:a.txt # look at old version of a.txt</pre><p>Search for regressions:</p><pre class="screen">$ git bisect start
|
||
$ git bisect bad # current version is bad
|
||
$ git bisect good v2.6.13-rc2 # last known good revision
|
||
Bisecting: 675 revisions left to test after this
|
||
# test here, then:
|
||
$ git bisect good # if this revision is good, or
|
||
$ git bisect bad # if this revision is bad.
|
||
# repeat until done.</pre></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="making-changes"></a>Chapter 61. Making changes</h2></div></div></div><p>Make sure Git knows who to blame:</p><pre class="screen">$ cat >>~/.gitconfig <<\EOF
|
||
[user]
|
||
name = Your Name Comes Here
|
||
email = you@yourdomain.example.com
|
||
EOF</pre><p>Select file contents to include in the next commit, then make the
|
||
commit:</p><pre class="screen">$ git add a.txt # updated file
|
||
$ git add b.txt # new file
|
||
$ git rm c.txt # old file
|
||
$ git commit</pre><p>Or, prepare and create the commit in one step:</p><pre class="screen">$ git commit d.txt # use latest content only of d.txt
|
||
$ git commit -a # use latest content of all tracked files</pre></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="merging"></a>Chapter 62. Merging</h2></div></div></div><pre class="screen">$ git merge test # merge branch "test" into the current branch
|
||
$ git pull git://example.com/project.git master
|
||
# fetch and merge in remote branch
|
||
$ git pull . test # equivalent to git merge test</pre></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="sharing-your-changes"></a>Chapter 63. Sharing your changes</h2></div></div></div><p>Importing or exporting patches:</p><pre class="screen">$ git format-patch origin..HEAD # format a patch for each commit
|
||
# in HEAD but not in origin
|
||
$ git am mbox # import patches from the mailbox "mbox"</pre><p>Fetch a branch in a different Git repository, then merge into the
|
||
current branch:</p><pre class="screen">$ git pull git://example.com/project.git theirbranch</pre><p>Store the fetched branch into a local branch before merging into the
|
||
current branch:</p><pre class="screen">$ git pull git://example.com/project.git theirbranch:mybranch</pre><p>After creating commits on a local branch, update the remote
|
||
branch with your commits:</p><pre class="screen">$ git push ssh://example.com/project.git mybranch:theirbranch</pre><p>When remote and local branch are both named "test":</p><pre class="screen">$ git push ssh://example.com/project.git test</pre><p>Shortcut version for a frequently used remote repository:</p><pre class="screen">$ git remote add example ssh://example.com/project.git
|
||
$ git push example test</pre></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="repository-maintenance"></a>Chapter 64. Repository maintenance</h2></div></div></div><p>Check for corruption:</p><pre class="screen">$ git fsck</pre><p>Recompress, remove unused cruft:</p><pre class="screen">$ git gc</pre></div></div><div class="part"><div class="titlepage"><div><div><h1 class="title"><a name="todo"></a>Part XIII. Appendix B: Notes and todo list for this manual</h1></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl class="toc"><dt><span class="chapter"><a href="#todo-list">65. Todo list</a></span></dt></dl></div><div class="chapter"><div class="titlepage"><div><div><h2 class="title"><a name="todo-list"></a>Chapter 65. Todo list</h2></div></div></div><p>This is a work in progress.</p><p>The basic requirements:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">It must be readable in order, from beginning to end, by someone
|
||
intelligent with a basic grasp of the UNIX command line, but without
|
||
any special knowledge of Git. If necessary, any other prerequisites
|
||
should be specifically mentioned as they arise.</li><li class="listitem">Whenever possible, section headings should clearly describe the task
|
||
they explain how to do, in language that requires no more knowledge
|
||
than necessary: for example, "importing patches into a project" rather
|
||
than "the <code class="literal">git am</code> command"</li></ul></div><p>Think about how to create a clear chapter dependency graph that will
|
||
allow people to get to important topics without necessarily reading
|
||
everything in between.</p><p>Scan <code class="literal">Documentation/</code> for other stuff left out; in particular:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">howto’s</li><li class="listitem">some of <code class="literal">technical/</code>?</li><li class="listitem">hooks</li><li class="listitem">list of commands in git(1)</li></ul></div><p>Scan email archives for other stuff left out</p><p>Scan man pages to see if any assume more background than this manual
|
||
provides.</p><p>Add more good examples. Entire sections of just cookbook examples
|
||
might be a good idea; maybe make an "advanced examples" section a
|
||
standard end-of-chapter section?</p><p>Include cross-references to the glossary, where appropriate.</p><p>Add a section on working with other version control systems, including
|
||
CVS, Subversion, and just imports of series of release tarballs.</p><p>Write a chapter on using plumbing and writing scripts.</p><p>Alternates, clone -reference, etc.</p><p>More on recovery from repository corruption. See:
|
||
<a class="ulink" href="http://marc.info/?l=git&m=117263864820799&w=2" target="_top">http://marc.info/?l=git&m=117263864820799&w=2</a>
|
||
<a class="ulink" href="http://marc.info/?l=git&m=117147855503798&w=2" target="_top">http://marc.info/?l=git&m=117147855503798&w=2</a></p></div></div></div></body></html>
|