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<h1 id="top">A Visual Git Reference</h1>
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<p id="link-to-png">If the images do not work, you can try the <a
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<p>This page gives brief, visual reference for the most common commands
in git. Once you know a bit about how git works, this site may solidify
your understanding. If you're interested in how this site was created, see
my <a href='http://github.com/MarkLodato/visual-git-guide'>GitHub
repository</a>.</p>
<p id="link-to-d3">Also recommended: <a
href="http://onlywei.github.io/explain-git-with-d3/#">Visualizing Git
Concepts with D3</a></p>
<h2 id="contents">Contents</h2>
<ol>
<li><a href="#basic-usage">Basic Usage</a></li>
<li><a href="#conventions">Conventions</a></li>
<li><a href="#commands-in-detail">Commands in Detail</a>
<ol>
<li><a href="#diff">Diff</a></li>
<li><a href="#commit">Commit</a></li>
<li><a href="#checkout">Checkout</a></li>
<li><a href="#detached">Committing with a Detached HEAD</a></li>
<li><a href="#reset">Reset</a></li>
<li><a href="#merge">Merge</a></li>
<li><a href="#cherry-pick">Cherry Pick</a></li>
<li><a href="#rebase">Rebase</a></li>
</ol>
</li>
<li><a href="#technical-notes">Technical Notes</a></li>
</ol>
<h2 id="basic-usage">Basic Usage</h2>
<div class="center"><img src='basic-usage.svg.png'></div>
<p>The four commands above copy files between the working directory, the
stage (also called the index), and the history (in the form of commits).</p>
<ul>
<li><code>git add <em>files</em></code> copies <em>files</em> (at their
current state) to the stage.</li>
<li><code>git commit</code> saves a snapshot of the stage as a
commit.</li>
<li><code>git reset -- <em>files</em></code> unstages files; that is, it
copies <em>files</em> from the latest commit to the stage. Use this
command to "undo" a <code>git add <em>files</em></code>. You can also
<code>git reset</code> to unstage everything.</li>
<li><code>git checkout -- <em>files</em></code> copies <em>files</em> from
the stage to the working directory. Use this to throw away local
changes.</li>
</ul>
<p>You can use <code>git reset -p</code>, <code>git checkout -p</code>, or
<code>git add -p</code> instead of (or in addition to) specifying particular
files to interactively choose which hunks copy.</p>
<p>It is also possible to jump over the stage and check out files directly
from the history or commit files without staging first.</p>
<div class="center"><img src='basic-usage-2.svg.png'></div>
<ul>
<li><code>git commit -a </code> is equivalent to running <tt>git add</tt>
on all filenames that existed in the latest commit, and then running
<tt>git commit</tt>.</li>
<li><code>git commit <em>files</em></code> creates a new commit containing
the contents of the latest commit, plus a snapshot of <em>files</em> taken
from the working directory. Additionally, <em>files</em> are copied to
the stage.</li>
<li><code>git checkout HEAD -- <em>files</em></code> copies <em>files</em>
from the latest commit to both the stage and the working directory.</li>
</ul>
<h2 id="conventions">Conventions</h2>
<p>In the rest of this document, we will use graphs of the following
form.</p>
<div class="center"><img src='conventions.svg.png'></div>
<p>Commits are shown in green as 5-character IDs, and they point to their
parents. Branches are shown in orange, and they point to particular
commits. The current branch is identified by the special reference
<em>HEAD</em>, which is "attached" to that branch. In this image, the five
latest commits are shown, with <em>ed489</em> being the most recent.
<em>master</em> (the current branch) points to this commit, while
<em>maint</em> (another branch) points to an ancestor of <em>master</em>'s
commit.</p>
<h2 id="commands-in-detail">Commands in Detail</h2>
<h3 id="diff">Diff</h3>
<p>There are various ways to look at differences between commits. Below are
some common examples. Any of these commands can optionally take extra
filename arguments that limit the differences to the named files.</p>
<div class="center"><img src='diff.svg.png'></div>
<h3 id="commit">Commit</h3>
<p>When you commit, git creates a new commit object using the files from the
stage and sets the parent to the current commit. It then points the current
branch to this new commit. In the image below, the current branch is
<em>master</em>. Before the command was run, <em>master</em> pointed to
<em>ed489</em>. Afterward, a new commit, <em>f0cec</em>, was created, with
parent <em>ed489</em>, and then <em>master</em> was moved to the new
commit.</p>
<div class="center"><img src='commit-master.svg.png'></div>
<p>This same process happens even when the current branch is an ancestor of
another. Below, a commit occurs on branch <em>maint</em>, which was an
ancestor of <em>master</em>, resulting in <em>1800b</em>. Afterward,
<em>maint</em> is no longer an ancestor of <em>master</em>. To join the two
histories, a <a href='#merge'>merge</a> (or <a href='#rebase'>rebase</a>)
will be necessary.</p>
<div class="center"><img src='commit-maint.svg.png'></div>
<p>Sometimes a mistake is made in a commit, but this is easy to correct with
<code>git commit --amend</code>. When you use this command, git creates a
new commit with the same parent as the current commit. (The old commit will
be discarded if nothing else references it.)</p>
<div class="center"><img src='commit-amend.svg.png'></div>
<p>A fourth case is committing with a <a href="#detached">detached
HEAD</a>, as explained later.</p>
<h3 id="checkout">Checkout</h3>
<p>The checkout command is used to copy files from the history (or stage) to
the working directory, and to optionally switch branches.</p>
<p>When a filename (and/or <code>-p</code>) is given, git copies those files
from the given commit to the stage and the working directory. For example,
<code>git checkout HEAD~ foo.c</code> copies the file <code>foo.c</code>
from the commit called <em>HEAD~</em> (the parent of the current commit) to
the working directory, and also stages it. (If no commit name is given,
files are copied from the stage.) Note that the current branch is not
changed.</p>
<div class="center"><img src='checkout-files.svg.png'></div>
<p>When a filename is <em>not</em> given but the reference is a (local)
branch, <em>HEAD</em> is moved to that branch (that is, we "switch to" that
branch), and then the stage and working directory are set to match the
contents of that commit. Any file that exists in the new commit
(<em>a47c3</em> below) is copied; any file that exists in the old commit
(<em>ed489</em>) but not in the new one is deleted; and any file that exists
in neither is ignored.</p>
<div class="center"><img src='checkout-branch.svg.png'></div>
<p>When a filename is <em>not</em> given and the reference is <em>not</em> a
(local) branch &mdash; say, it is a tag, a remote branch, a SHA-1 ID, or
something like <em>master~3</em> &mdash; we get an anonymous branch, called
a <em>detached HEAD</em>. This is useful for jumping around the history.
Say you want to compile version 1.6.6.1 of git. You can <code>git checkout
v1.6.6.1</code> (which is a tag, not a branch), compile, install, and then
switch back to another branch, say <code>git checkout master</code>.
However, committing works slightly differently with a detached HEAD; this is
covered <a href="#detached">below</a>.</p>
<div class="center"><img src='checkout-detached.svg.png'></div>
<h3 id="detached">Committing with a Detached HEAD</h3>
<p>When <em>HEAD</em> is detached, commits work like normal, except no named
branch gets updated. (You can think of this as an anonymous branch.)</p>
<div class="center"><img src='commit-detached.svg.png'></div>
<p>Once you check out something else, say <em>master</em>, the commit is
(presumably) no longer referenced by anything else, and gets lost. Note
that after the command, there is nothing referencing <em>2eecb</em>.</p>
<div class="center"><img src='checkout-after-detached.svg.png'></div>
<p>If, on the other hand, you want to save this state, you can create a new
named branch using <code>git checkout -b <em>name</em></code>.</p>
<div class="center"><img src='checkout-b-detached.svg.png'></div>
<h3 id="reset">Reset</h3>
<p>The reset command moves the current branch to another position, and
optionally updates the stage and the working directory. It also is used to
copy files from the history to the stage without touching the working
directory.</p>
<p>If a commit is given with no filenames, the current branch is moved to
that commit, and then the stage is updated to match this commit. If
<code>--hard</code> is given, the working directory is also updated. If
<code>--soft</code> is given, neither is updated.</p>
<div class="center"><img src='reset-commit.svg.png'></div>
<p>If a commit is not given, it defaults to <em>HEAD</em>. In this case,
the branch is not moved, but the stage (and optionally the working
directory, if <code>--hard</code> is given) are reset to the contents of the
last commit.</p>
<div class="center"><img src='reset.svg.png'></div>
<p>If a filename (and/or <code>-p</code>) is given, then the command works
similarly to <a href='#checkout'>checkout</a> with a filename, except only
the stage (and not the working directory) is updated. (You may also specify
the commit from which to take files, rather than <em>HEAD</em>.)</p>
<div class="center"><img src='reset-files.svg.png'></div>
<h3 id="merge">Merge</h3>
<p>A merge creates a new commit that incorporates changes from other
commits. Before merging, the stage must match the current commit. The
trivial case is if the other commit is an ancestor of the current commit, in
which case nothing is done. The next most simple is if the current commit
is an ancestor of the other commit. This results in a <em>fast-forward</em>
merge. The reference is simply moved, and then the new commit is checked
out.</p>
<div class="center"><img src='merge-ff.svg.png'></div>
<p>Otherwise, a "real" merge must occur. You can choose other strategies,
but the default is to perform a "recursive" merge, which basically takes the
current commit (<em>ed489</em> below), the other commit (<em>33104</em>),
and their common ancestor (<em>b325c</em>), and performs a <a
href='http://en.wikipedia.org/wiki/Three-way_merge'>three-way merge</a>.
The result is saved to the working directory and the stage, and then a
commit occurs, with an extra parent (<em>33104</em>) for the new commit.
</p>
<div class="center"><img src='merge.svg.png'></div>
<h3 id="cherry-pick">Cherry Pick</h3>
<p>The cherry-pick command "copies" a commit, creating a new commit on the
current branch with the same message and patch as another commit.</p>
<div class="center"><img src='cherry-pick.svg.png'></div>
<h3 id="rebase">Rebase</h3>
<p>A rebase is an alternative to a <a href='#merge'>merge</a> for combining
multiple branches. Whereas a merge creates a single commit with two
parents, leaving a non-linear history, a rebase replays the commits from the
current branch onto another, leaving a linear history. In essence, this is
an automated way of performing several <a
href='#cherry-pick'>cherry-pick</a>s in a row.</p>
<div class="center"><img src='rebase.svg.png'></div>
<p>The above command takes all the commits that exist in <em>topic</em> but
not in <em>master</em> (namely <em>169a6</em> and <em>2c33a</em>), replays
them onto <em>master</em>, and then moves the branch head to the new tip.
Note that the old commits will be garbage collected if they are no longer
referenced.</p>
<p>To limit how far back to go, use the <code>--onto</code> option. The
following command replays onto <em>master</em> the most recent commits on
the current branch since <em>169a6</em> (exclusive), namely
<em>2c33a</em>.</p>
<div class="center"><img src='rebase-onto.svg.png'></div>
<p>There is also <code>git rebase --interactive</code>, which allows one to
do more complicated things than simply replaying commits, namely dropping,
reordering, modifying, and squashing commits. There is no obvious picture
to draw for this; see <a
href='http://www.kernel.org/pub/software/scm/git/docs/git-rebase.html#_interactive_mode'>git-rebase(1)</a>
for more details.</p>
<h2 id="technical-notes">Technical Notes</h2>
<p>The contents of files are not actually stored in the index
(<em>.git/index</em>) or in commit objects. Rather, each file is stored in
the object database (<em>.git/objects</em>) as a <em>blob</em>, identified
by its SHA-1 hash. The index file lists the filenames along with the
identifier of the associated blob, as well as some other data. For commits,
there is an additional data type, a <em>tree</em>, also identified by its
hash. Trees correspond to directories in the working directory, and contain
a list of trees and blobs corresponding to each filename within that
directory. Each commit stores the identifier of its top-level tree, which
in turn contains all of the blobs and other trees associated with that
commit.</p>
<p>If you make a commit using a detached HEAD, the last commit really is
referenced by something: the reflog for HEAD. However, this will expire
after a while, so the commit will eventually be garbage collected, similar
to commits discarded with <code>git commit --amend</code> or <code>git
rebase</code>.</p>
<hr>
<p>Copyright &copy; 2010,
<a href='mailto:lodatom@gmail.com'>Mark Lodato</a>.
Japanese translation &copy; 2010,
<a href='http://github.com/kazu-yamamoto'>Kazu Yamamoto</a>.
Korean translation &copy; 2011,
<a href='mailto:sean@weaveus.com'>Sean Lee</a>.
Russian translation &copy; 2012,
<a href='mailto:alex@sychev.com'>Alex Sychev</a>.
French translation &copy; 2012,
<a href='mailto:michel.lefranc@gmail.com'>Michel Lefranc</a>.
Chinese translation &copy; 2012,
<a href='mailto:ellrywych@gmail.com'>wych</a>.
Spanish translation &copy; 2012,
<a href='http://www.delucas.com.ar'>Lucas Videla</a>.
Italian translation &copy; 2012,
<a href="mailto:daniel.londero@gmail.com">Daniel Londero</a>.
German translation &copy; 2013,
<a href="mailto:mafulafunk@gmail.com">Martin Funk</a>.
Slovak translation &copy; 2013,
<a href='https://github.com/llucenic'>Ľudovít Lučenič</a>.
Portuguese translation &copy; 2014,
<a href='mailto:goliveira5d@gmail.com'>Gustavo de Oliveira</a>
Traditional Chinese translation &copy; 2015,
<a href='https://github.com/PeterDaveHello'>Peter Dave Hello</a>
</p>
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href="https://creativecommons.org/licenses/by-nc-sa/3.0/us/">Creative
Commons Attribution-Noncommercial-Share Alike 3.0 United States
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