git-range-diff(1) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | OUTPUT STABILITY | CONFIGURATION | EXAMPLES | ALGORITHM | SEE ALSO | GIT | COLOPHON

GIT-RANGE-DIFF(1)              Git Manual              GIT-RANGE-DIFF(1)

NAME         top

       git-range-diff - Compare two commit ranges (e.g. two versions of
       a branch)

SYNOPSIS         top

       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> )

DESCRIPTION         top

       This command shows the differences between two versions of a
       patch series, or more generally, two commit ranges (ignoring
       merge commits).

       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>.

OPTIONS         top

       --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 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.

OUTPUT STABILITY         top

       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).

CONFIGURATION         top

       This command uses the diff.color.* and pager.range-diff settings
       (the latter is on by default). See git-config(1).

EXAMPLES         top

       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 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.

ALGORITHM         top

       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

SEE ALSO         top

       git-log(1)

GIT         top

       Part of the git(1) suite

COLOPHON         top

       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 2021-06-20.  (At that time,
       the date of the most recent commit that was found in the
       repository was 2021-06-14.)  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 2.32.0.93.g670b81a         06/17/2021              GIT-RANGE-DIFF(1)

Pages that refer to this page: git(1)git-config(1)git-format-patch(1)