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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OUTPUT STABILITY | CONFIGURATION | EXAMPLES | ALGORITHM | SEE ALSO | GIT | COLOPHON |
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GIT-RANGE-DIFF(1) Git Manual GIT-RANGE-DIFF(1)
git-range-diff - Compare two commit ranges (e.g. two versions of
a branch)
git range-diff [--color=[<when>]] [--no-color] [<diff-options>]
[--no-dual-color] [--creation-factor=<factor>]
[--left-only | --right-only]
( <range1> <range2> | <rev1>...<rev2> | <base> <rev1> <rev2> )
[[--] <path>...]
This command shows the differences between two versions of a
patch series, or more generally, two commit ranges (ignoring
merge commits).
In the presence of <path> arguments, these commit ranges are
limited accordingly.
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.
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.
There are three ways to specify the commit ranges:
• <range1> <range2>: Either commit range can be of the form
<base>..<rev>, <rev>^! or <rev>^-<n>. See SPECIFYING RANGES
in gitrevisions(7) for more details.
• <rev1>...<rev2>. This is equivalent to <rev2>..<rev1>
<rev1>..<rev2>.
• <base> <rev1> <rev2>: This is equivalent to <base>..<rev1>
<base>..<rev2>.
--no-dual-color
When the commit diffs differ, ‘git range-diff` recreates the
original diffs’ coloring, and adds outer -/+ diff markers
with the background being red/green to make it easier to see
e.g. when there was a change in what exact lines were added.
Additionally, the commit diff lines that are only present in
the first commit range are shown "dimmed" (this can be
overridden using the color.diff.<slot> config setting where
<slot> is one of contextDimmed, oldDimmed and newDimmed), 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 color.diff.<slot> with <slot> being one
of contextBold, oldBold or newBold).
This is known to range-diff as "dual coloring". Use
--no-dual-color to revert to color all lines according to the
outer diff markers (and completely ignore the inner diff when
it comes to color).
--creation-factor=<percent>
Set the creation/deletion cost fudge factor to <percent>.
Defaults to 60. Try a larger value if git range-diff
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.
--left-only
Suppress commits that are missing from the first specified
range (or the "left range" when using the <rev1>...<rev2>
format).
--right-only
Suppress commits that are missing from the second specified
range (or the "right range" when using the <rev1>...<rev2>
format).
--[no-]notes[=<ref>]
This flag is passed to the git log program (see git-log(1))
that generates the patches.
<range1> <range2>
Compare the commits specified by the two ranges, where
<range1> is considered an older version of <range2>.
<rev1>...<rev2>
Equivalent to passing <rev2>..<rev1> and <rev1>..<rev2>.
<base> <rev1> <rev2>
Equivalent to passing <base>..<rev1> and <base>..<rev2>. Note
that <base> does not need to be the exact branch point of the
branches. Example: after rebasing a branch my-topic, git
range-diff my-topic@{u} my-topic@{1} my-topic would show the
differences introduced by the rebase.
git range-diff also accepts the regular diff options (see
git-diff(1)), most notably the --color=[<when>] and --no-color
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 git log when generating
those patches.
The output of the range-diff 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
range-diff (as opposed to something like the --stable option to
git-patch-id(1)). There’s also no equivalent of git-apply(1) for
range-diff, the output is not intended to be machine-readable.
This is particularly true when passing in diff options. Currently
some options like --stat can, as an emergent effect, produce
output that’s quite useless in the context of range-diff. Future
versions of range-diff may learn to interpret such options in a
manner specific to range-diff (e.g. for --stat producing
human-readable output which summarizes how the diffstat changed).
This command uses the diff.color.* and pager.range-diff settings
(the latter is on by default). See git-config(1).
When a rebase required merge conflicts to be resolved, compare
the changes introduced by the rebase directly afterwards using:
$ git range-diff @{u} @{1} @
A typical output of git range-diff would look like this:
-: ------- > 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
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.
When the output goes to a terminal, it is color-coded by default,
just like regular git diff'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 git show's output, and the third line colors the
old commit red, the new one green and the rest like git show's
commit header.
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.
To help with that, range uses the --dual-color 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
background red or green, to make it more obvious that they
describe how the diff itself changed.
The general idea is this: we generate a cost matrix between the
commits in both commit ranges, then solve the least-cost
assignment.
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.
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.
Example: Let commits 1--2 be the first iteration of a patch
series and A--C the second iteration. Let’s assume that A is a
cherry-pick of 2, and C is a cherry-pick of 1 but with a small
modification (say, a fixed typo). Visualize the commits as a
bipartite graph:
1 A
2 B
C
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:
1 A
/
2 --------' B
C
This explanation comes for "free" because there was no change.
Similarly C could be explained using 1, but that comes at some
cost c>0 because of the modification:
1 ----. A
| /
2 ----+---' B
|
`----- C
c>0
In mathematical terms, what we are looking for is some sort of a
minimum cost bipartite matching; ‘1` is matched to C 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:
1 ----. A
| /
2 ----+---' B
|
o `----- C
c>0
o o
o o
The cost of an edge o--C is the size of C's diff, modified by a
fudge factor that should be smaller than 100%. The cost of an
edge o--o is free. The fudge factor is necessary because even if
1 and C have nothing in common, they may still share a few empty
lines and such, possibly making the assignment 1--C, o--o
slightly cheaper than 1--o, o--C even if 1 and C have nothing in
common. With the fudge factor we require a much larger common
part to consider patches as corresponding.
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:
1 ----. A
| /
2 ----+---' B
.--+-----'
o -' `----- C
c>0
o ---------- o
o ---------- o
git-log(1)
Part of the git(1) suite
This page is part of the git (Git distributed version control
system) project. Information about the project can be found at
⟨http://git-scm.com/⟩. If you have a bug report for this manual
page, see ⟨http://git-scm.com/community⟩. This page was obtained
from the project's upstream Git repository
⟨https://github.com/git/git.git⟩ on 2023-12-22. (At that time,
the date of the most recent commit that was found in the
repository was 2023-12-20.) If you discover any rendering
problems in this HTML version of the page, or you believe there
is a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
Git 2.43.0.174.g055bb6 2023-12-20 GIT-RANGE-DIFF(1)
Pages that refer to this page: git(1), git-config(1), git-format-patch(1), stg-email(1)
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HTML rendering created 2023-12-22 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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