6 git-range-diff - Compare two commit ranges (e.g. two versions of a branch)
11 'git range-diff' [--color=[<when>]] [--no-color] [<diff-options>]
12 [--no-dual-color] [--creation-factor=<factor>]
13 ( <range1> <range2> | <rev1>...<rev2> | <base> <rev1> <rev2> )
18 This command shows the differences between two versions of a patch
19 series, or more generally, two commit ranges (ignoring merge commits).
21 To that end, it first finds pairs of commits from both commit ranges
22 that correspond with each other. Two commits are said to correspond when
23 the diff between their patches (i.e. the author information, the commit
24 message and the commit diff) is reasonably small compared to the
25 patches' size. See ``Algorithm`` below for details.
27 Finally, the list of matching commits is shown in the order of the
28 second commit range, with unmatched commits being inserted just after
29 all of their ancestors have been shown.
35 When the commit diffs differ, `git range-diff` recreates the
36 original diffs' coloring, and adds outer -/+ diff markers with
37 the *background* being red/green to make it easier to see e.g.
38 when there was a change in what exact lines were added.
40 Additionally, the commit diff lines that are only present in the first commit
41 range are shown "dimmed" (this can be overridden using the `color.diff.<slot>`
42 config setting where `<slot>` is one of `contextDimmed`, `oldDimmed` and
43 `newDimmed`), and the commit diff lines that are only present in the second
44 commit range are shown in bold (which can be overridden using the config
45 settings `color.diff.<slot>` with `<slot>` being one of `contextBold`,
46 `oldBold` or `newBold`).
48 This is known to `range-diff` as "dual coloring". Use `--no-dual-color`
49 to revert to color all lines according to the outer diff markers
50 (and completely ignore the inner diff when it comes to color).
52 --creation-factor=<percent>::
53 Set the creation/deletion cost fudge factor to `<percent>`.
54 Defaults to 60. Try a larger value if `git range-diff` erroneously
55 considers a large change a total rewrite (deletion of one commit
56 and addition of another), and a smaller one in the reverse case.
57 See the ``Algorithm`` section below for an explanation why this is
61 Compare the commits specified by the two ranges, where
62 `<range1>` is considered an older version of `<range2>`.
65 Equivalent to passing `<rev2>..<rev1>` and `<rev1>..<rev2>`.
67 <base> <rev1> <rev2>::
68 Equivalent to passing `<base>..<rev1>` and `<base>..<rev2>`.
69 Note that `<base>` does not need to be the exact branch point
70 of the branches. Example: after rebasing a branch `my-topic`,
71 `git range-diff my-topic@{u} my-topic@{1} my-topic` would
72 show the differences introduced by the rebase.
74 `git range-diff` also accepts the regular diff options (see
75 linkgit:git-diff[1]), most notably the `--color=[<when>]` and
76 `--no-color` options. These options are used when generating the "diff
77 between patches", i.e. to compare the author, commit message and diff of
78 corresponding old/new commits. There is currently no means to tweak the
79 diff options passed to `git log` when generating those patches.
84 The output of the `range-diff` command is subject to change. It is
85 intended to be human-readable porcelain output, not something that can
86 be used across versions of Git to get a textually stable `range-diff`
87 (as opposed to something like the `--stable` option to
88 linkgit:git-patch-id[1]). There's also no equivalent of
89 linkgit:git-apply[1] for `range-diff`, the output is not intended to
92 This is particularly true when passing in diff options. Currently some
93 options like `--stat` can, as an emergent effect, produce output
94 that's quite useless in the context of `range-diff`. Future versions
95 of `range-diff` may learn to interpret such options in a manner
96 specific to `range-diff` (e.g. for `--stat` producing human-readable
97 output which summarizes how the diffstat changed).
101 This command uses the `diff.color.*` and `pager.range-diff` settings
102 (the latter is on by default).
103 See linkgit:git-config[1].
109 When a rebase required merge conflicts to be resolved, compare the changes
110 introduced by the rebase directly afterwards using:
113 $ git range-diff @{u} @{1} @
117 A typical output of `git range-diff` would look like this:
120 -: ------- > 1: 0ddba11 Prepare for the inevitable!
121 1: c0debee = 2: cab005e Add a helpful message at the start
122 2: f00dbal ! 3: decafe1 Describe a bug
124 Author: A U Thor <author@example.com>
126 -TODO: Describe a bug
131 -+What is unexpected is that it will also crash.
132 ++Unexpectedly, it also crashes. This is a bug, and the jury is
133 ++still out there how to fix it best. See ticket #314 for details.
136 3: bedead < -: ------- TO-UNDO
139 In this example, there are 3 old and 3 new commits, where the developer
140 removed the 3rd, added a new one before the first two, and modified the
141 commit message of the 2nd commit as well its diff.
143 When the output goes to a terminal, it is color-coded by default, just
144 like regular `git diff`'s output. In addition, the first line (adding a
145 commit) is green, the last line (deleting a commit) is red, the second
146 line (with a perfect match) is yellow like the commit header of `git
147 show`'s output, and the third line colors the old commit red, the new
148 one green and the rest like `git show`'s commit header.
150 A naive color-coded diff of diffs is actually a bit hard to read,
151 though, as it colors the entire lines red or green. The line that added
152 "What is unexpected" in the old commit, for example, is completely red,
153 even if the intent of the old commit was to add something.
155 To help with that, `range` uses the `--dual-color` mode by default. In
156 this mode, the diff of diffs will retain the original diff colors, and
157 prefix the lines with -/+ markers that have their *background* red or
158 green, to make it more obvious that they describe how the diff itself
165 The general idea is this: we generate a cost matrix between the commits
166 in both commit ranges, then solve the least-cost assignment.
168 The cost matrix is populated thusly: for each pair of commits, both
169 diffs are generated and the "diff of diffs" is generated, with 3 context
170 lines, then the number of lines in that diff is used as cost.
172 To avoid false positives (e.g. when a patch has been removed, and an
173 unrelated patch has been added between two iterations of the same patch
174 series), the cost matrix is extended to allow for that, by adding
175 fixed-cost entries for wholesale deletes/adds.
177 Example: Let commits `1--2` be the first iteration of a patch series and
178 `A--C` the second iteration. Let's assume that `A` is a cherry-pick of
179 `2,` and `C` is a cherry-pick of `1` but with a small modification (say,
180 a fixed typo). Visualize the commits as a bipartite graph:
190 We are looking for a "best" explanation of the new series in terms of
191 the old one. We can represent an "explanation" as an edge in the graph:
202 This explanation comes for "free" because there was no change. Similarly
203 `C` could be explained using `1`, but that comes at some cost c>0
204 because of the modification:
215 In mathematical terms, what we are looking for is some sort of a minimum
216 cost bipartite matching; `1` is matched to `C` at some cost, etc. The
217 underlying graph is in fact a complete bipartite graph; the cost we
218 associate with every edge is the size of the diff between the two
219 commits' patches. To explain also new commits, we introduce dummy nodes
234 The cost of an edge `o--C` is the size of `C`'s diff, modified by a
235 fudge factor that should be smaller than 100%. The cost of an edge
236 `o--o` is free. The fudge factor is necessary because even if `1` and
237 `C` have nothing in common, they may still share a few empty lines and
238 such, possibly making the assignment `1--C`, `o--o` slightly cheaper
239 than `1--o`, `o--C` even if `1` and `C` have nothing in common. With the
240 fudge factor we require a much larger common part to consider patches as
243 The overall time needed to compute this algorithm is the time needed to
244 compute n+m commit diffs and then n*m diffs of patches, plus the time
245 needed to compute the least-cost assigment between n and m diffs. Git
246 uses an implementation of the Jonker-Volgenant algorithm to solve the
247 assignment problem, which has cubic runtime complexity. The matching
248 found in this case will look like this:
269 Part of the linkgit:git[1] suite
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