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<body class="manpage">
<div id="header">
<h1>
git-range-diff(1) Manual Page
</h1>
<h2>NAME</h2>
<div class="sectionbody">
<p>git-range-diff -
Compare two commit ranges (e.g. two versions of a branch)
</p>
</div>
</div>
<div id="content">
<div class="sect1">
<h2 id="_synopsis">SYNOPSIS</h2>
<div class="sectionbody">
<div class="verseblock">
<pre class="content"><em>git range-diff</em> [--color=[<when>]] [--no-color] [<diff-options>]
[--no-dual-color] [--creation-factor=<factor>]
[--left-only | --right-only]
( <range1> <range2> | <rev1>…<rev2> | <base> <rev1> <rev2> )
[[--] <path>…]</pre>
<div class="attribution">
</div></div>
</div>
</div>
<div class="sect1">
<h2 id="_description">DESCRIPTION</h2>
<div class="sectionbody">
<div class="paragraph"><p>This command shows the differences between two versions of a patch
series, or more generally, two commit ranges (ignoring merge commits).</p></div>
<div class="paragraph"><p>In the presence of <code><path></code> arguments, these commit ranges are limited
accordingly.</p></div>
<div class="paragraph"><p>To that end, it first finds pairs of commits from both commit ranges
that correspond with each other. Two commits are said to correspond when
the diff between their patches (i.e. the author information, the commit
message and the commit diff) is reasonably small compared to the
patches' size. See ``Algorithm`` below for details.</p></div>
<div class="paragraph"><p>Finally, the list of matching commits is shown in the order of the
second commit range, with unmatched commits being inserted just after
all of their ancestors have been shown.</p></div>
<div class="paragraph"><p>There are three ways to specify the commit ranges:</p></div>
<div class="ulist"><ul>
<li>
<p>
<code><range1> <range2></code>: Either commit range can be of the form
<code><base>..<rev></code>, <code><rev>^!</code> or <code><rev>^-<n></code>. See <code>SPECIFYING RANGES</code>
in <a href="gitrevisions.html">gitrevisions(7)</a> for more details.
</p>
</li>
<li>
<p>
<code><rev1>...<rev2></code>. This is equivalent to
<code><rev2>..<rev1> <rev1>..<rev2></code>.
</p>
</li>
<li>
<p>
<code><base> <rev1> <rev2></code>: This is equivalent to <code><base>..<rev1>
<base>..<rev2></code>.
</p>
</li>
</ul></div>
</div>
</div>
<div class="sect1">
<h2 id="_options">OPTIONS</h2>
<div class="sectionbody">
<div class="dlist"><dl>
<dt class="hdlist1">
--no-dual-color
</dt>
<dd>
<p>
When the commit diffs differ, ‘git range-diff` recreates the
original diffs’ coloring, and adds outer -/+ diff markers with
the <strong>background</strong> being red/green to make it easier to see e.g.
when there was a change in what exact lines were added.
</p>
<div class="paragraph"><p>Additionally, the commit diff lines that are only present in the first commit
range are shown "dimmed" (this can be overridden using the <code>color.diff.<slot></code>
config setting where <code><slot></code> is one of <code>contextDimmed</code>, <code>oldDimmed</code> and
<code>newDimmed</code>), and the commit diff lines that are only present in the second
commit range are shown in bold (which can be overridden using the config
settings <code>color.diff.<slot></code> with <code><slot></code> being one of <code>contextBold</code>,
<code>oldBold</code> or <code>newBold</code>).</p></div>
<div class="paragraph"><p>This is known to <code>range-diff</code> as "dual coloring". Use <code>--no-dual-color</code>
to revert to color all lines according to the outer diff markers
(and completely ignore the inner diff when it comes to color).</p></div>
</dd>
<dt class="hdlist1">
--creation-factor=<percent>
</dt>
<dd>
<p>
Set the creation/deletion cost fudge factor to <code><percent></code>.
Defaults to 60. Try a larger value if <code>git range-diff</code> erroneously
considers a large change a total rewrite (deletion of one commit
and addition of another), and a smaller one in the reverse case.
See the ``Algorithm`` section below for an explanation of why this is
needed.
</p>
</dd>
<dt class="hdlist1">
--left-only
</dt>
<dd>
<p>
Suppress commits that are missing from the first specified range
(or the "left range" when using the <code><rev1>...<rev2></code> format).
</p>
</dd>
<dt class="hdlist1">
--right-only
</dt>
<dd>
<p>
Suppress commits that are missing from the second specified range
(or the "right range" when using the <code><rev1>...<rev2></code> format).
</p>
</dd>
<dt class="hdlist1">
--[no-]notes[=<ref>]
</dt>
<dd>
<p>
This flag is passed to the <code>git log</code> program
(see <a href="git-log.html">git-log(1)</a>) that generates the patches.
</p>
</dd>
<dt class="hdlist1">
<range1> <range2>
</dt>
<dd>
<p>
Compare the commits specified by the two ranges, where
<code><range1></code> is considered an older version of <code><range2></code>.
</p>
</dd>
<dt class="hdlist1">
<rev1>…<rev2>
</dt>
<dd>
<p>
Equivalent to passing <code><rev2>..<rev1></code> and <code><rev1>..<rev2></code>.
</p>
</dd>
<dt class="hdlist1">
<base> <rev1> <rev2>
</dt>
<dd>
<p>
Equivalent to passing <code><base>..<rev1></code> and <code><base>..<rev2></code>.
Note that <code><base></code> does not need to be the exact branch point
of the branches. Example: after rebasing a branch <code>my-topic</code>,
<code>git range-diff my-topic@{u} my-topic@{1} my-topic</code> would
show the differences introduced by the rebase.
</p>
</dd>
</dl></div>
<div class="paragraph"><p><code>git range-diff</code> also accepts the regular diff options (see
<a href="git-diff.html">git-diff(1)</a>), most notably the <code>--color=[<when>]</code> and
<code>--no-color</code> options. These options are used when generating the "diff
between patches", i.e. to compare the author, commit message and diff of
corresponding old/new commits. There is currently no means to tweak most of the
diff options passed to <code>git log</code> when generating those patches.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_output_stability">OUTPUT STABILITY</h2>
<div class="sectionbody">
<div class="paragraph"><p>The output of the <code>range-diff</code> command is subject to change. It is
intended to be human-readable porcelain output, not something that can
be used across versions of Git to get a textually stable <code>range-diff</code>
(as opposed to something like the <code>--stable</code> option to
<a href="git-patch-id.html">git-patch-id(1)</a>). There’s also no equivalent of
<a href="git-apply.html">git-apply(1)</a> for <code>range-diff</code>, the output is not intended to
be machine-readable.</p></div>
<div class="paragraph"><p>This is particularly true when passing in diff options. Currently some
options like <code>--stat</code> can, as an emergent effect, produce output
that’s quite useless in the context of <code>range-diff</code>. Future versions
of <code>range-diff</code> may learn to interpret such options in a manner
specific to <code>range-diff</code> (e.g. for <code>--stat</code> producing human-readable
output which summarizes how the diffstat changed).</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_configuration">CONFIGURATION</h2>
<div class="sectionbody">
<div class="paragraph"><p>This command uses the <code>diff.color.*</code> and <code>pager.range-diff</code> settings
(the latter is on by default).
See <a href="git-config.html">git-config(1)</a>.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_examples">EXAMPLES</h2>
<div class="sectionbody">
<div class="paragraph"><p>When a rebase required merge conflicts to be resolved, compare the changes
introduced by the rebase directly afterwards using:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>$ git range-diff @{u} @{1} @</code></pre>
</div></div>
<div class="paragraph"><p>A typical output of <code>git range-diff</code> would look like this:</p></div>
<div class="listingblock">
<div class="content">
<pre><code>-: ------- > 1: 0ddba11 Prepare for the inevitable!
1: c0debee = 2: cab005e Add a helpful message at the start
2: f00dbal ! 3: decafe1 Describe a bug
@@ -1,3 +1,3 @@
Author: A U Thor <author@example.com>
-TODO: Describe a bug
+Describe a bug
@@ -324,5 +324,6
This is expected.
-+What is unexpected is that it will also crash.
++Unexpectedly, it also crashes. This is a bug, and the jury is
++still out there how to fix it best. See ticket #314 for details.
Contact
3: bedead < -: ------- TO-UNDO</code></pre>
</div></div>
<div class="paragraph"><p>In this example, there are 3 old and 3 new commits, where the developer
removed the 3rd, added a new one before the first two, and modified the
commit message of the 2nd commit as well as its diff.</p></div>
<div class="paragraph"><p>When the output goes to a terminal, it is color-coded by default, just
like regular <code>git diff</code>'s output. In addition, the first line (adding a
commit) is green, the last line (deleting a commit) is red, the second
line (with a perfect match) is yellow like the commit header of <code>git
show</code>'s output, and the third line colors the old commit red, the new
one green and the rest like <code>git show</code>'s commit header.</p></div>
<div class="paragraph"><p>A naive color-coded diff of diffs is actually a bit hard to read,
though, as it colors the entire lines red or green. The line that added
"What is unexpected" in the old commit, for example, is completely red,
even if the intent of the old commit was to add something.</p></div>
<div class="paragraph"><p>To help with that, <code>range</code> uses the <code>--dual-color</code> mode by default. In
this mode, the diff of diffs will retain the original diff colors, and
prefix the lines with -/+ markers that have their <strong>background</strong> red or
green, to make it more obvious that they describe how the diff itself
changed.</p></div>
</div>
</div>
<div class="sect1">
<h2 id="_algorithm">Algorithm</h2>
<div class="sectionbody">
<div class="paragraph"><p>The general idea is this: we generate a cost matrix between the commits
in both commit ranges, then solve the least-cost assignment.</p></div>
<div class="paragraph"><p>The cost matrix is populated thusly: for each pair of commits, both
diffs are generated and the "diff of diffs" is generated, with 3 context
lines, then the number of lines in that diff is used as cost.</p></div>
<div class="paragraph"><p>To avoid false positives (e.g. when a patch has been removed, and an
unrelated patch has been added between two iterations of the same patch
series), the cost matrix is extended to allow for that, by adding
fixed-cost entries for wholesale deletes/adds.</p></div>
<div class="paragraph"><p>Example: Let commits <code>1--2</code> be the first iteration of a patch series and
<code>A--C</code> the second iteration. Let’s assume that <code>A</code> is a cherry-pick of
<code>2,</code> and <code>C</code> is a cherry-pick of <code>1</code> but with a small modification (say,
a fixed typo). Visualize the commits as a bipartite graph:</p></div>
<div class="listingblock">
<div class="content">
<pre><code> 1 A
2 B
C</code></pre>
</div></div>
<div class="paragraph"><p>We are looking for a "best" explanation of the new series in terms of
the old one. We can represent an "explanation" as an edge in the graph:</p></div>
<div class="listingblock">
<div class="content">
<pre><code> 1 A
/
2 --------' B
C</code></pre>
</div></div>
<div class="paragraph"><p>This explanation comes for "free" because there was no change. Similarly
<code>C</code> could be explained using <code>1</code>, but that comes at some cost c>0
because of the modification:</p></div>
<div class="listingblock">
<div class="content">
<pre><code> 1 ----. A
| /
2 ----+---' B
|
`----- C
c>0</code></pre>
</div></div>
<div class="paragraph"><p>In mathematical terms, what we are looking for is some sort of a minimum
cost bipartite matching; ‘1` is matched to <code>C</code> at some cost, etc. The
underlying graph is in fact a complete bipartite graph; the cost we
associate with every edge is the size of the diff between the two
commits’ patches. To explain also new commits, we introduce dummy nodes
on both sides:</p></div>
<div class="listingblock">
<div class="content">
<pre><code> 1 ----. A
| /
2 ----+---' B
|
o `----- C
c>0
o o
o o</code></pre>
</div></div>
<div class="paragraph"><p>The cost of an edge <code>o--C</code> is the size of <code>C</code>'s diff, modified by a
fudge factor that should be smaller than 100%. The cost of an edge
<code>o--o</code> is free. The fudge factor is necessary because even if <code>1</code> and
<code>C</code> have nothing in common, they may still share a few empty lines and
such, possibly making the assignment <code>1--C</code>, <code>o--o</code> slightly cheaper
than <code>1--o</code>, <code>o--C</code> even if <code>1</code> and <code>C</code> have nothing in common. With the
fudge factor we require a much larger common part to consider patches as
corresponding.</p></div>
<div class="paragraph"><p>The overall time needed to compute this algorithm is the time needed to
compute n+m commit diffs and then n*m diffs of patches, plus the time
needed to compute the least-cost assignment between n and m diffs. Git
uses an implementation of the Jonker-Volgenant algorithm to solve the
assignment problem, which has cubic runtime complexity. The matching
found in this case will look like this:</p></div>
<div class="listingblock">
<div class="content">
<pre><code> 1 ----. A
| /
2 ----+---' B
.--+-----'
o -' `----- C
c>0
o ---------- o
o ---------- o</code></pre>
</div></div>
</div>
</div>
<div class="sect1">
<h2 id="_see_also">SEE ALSO</h2>
<div class="sectionbody">
<div class="paragraph"><p><a href="git-log.html">git-log(1)</a></p></div>
</div>
</div>
<div class="sect1">
<h2 id="_git">GIT</h2>
<div class="sectionbody">
<div class="paragraph"><p>Part of the <a href="git.html">git(1)</a> suite</p></div>
</div>
</div>
</div>
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