1GIT-RANGE-DIFF(1) Git Manual GIT-RANGE-DIFF(1)
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6 git-range-diff - Compare two commit ranges (e.g. two versions of a
7 branch)
8
10 git range-diff [--color=[<when>]] [--no-color] [<diff-options>]
11 [--no-dual-color] [--creation-factor=<factor>]
12 [--left-only | --right-only]
13 ( <range1> <range2> | <rev1>...<rev2> | <base> <rev1> <rev2> )
14 [[--] <path>...]
15
17 This command shows the differences between two versions of a patch
18 series, or more generally, two commit ranges (ignoring merge commits).
19 In the presence of <path> arguments, these commit ranges are limited
21 accordingly.
22 To that end, it first finds pairs of commits from both commit ranges
24 that correspond with each other. Two commits are said to correspond
25 when the diff between their patches (i.e. the author information, the
26 commit message and the commit diff) is reasonably small compared to the
27 patches' size. See ``Algorithm`` below for details.
28 Finally, the list of matching commits is shown in the order of the
30 second commit range, with unmatched commits being inserted just after
31 all of their ancestors have been shown.
32 There are three ways to specify the commit ranges:
34 • <range1> <range2>: Either commit range can be of the form
36 <base>..<rev>, <rev>^! or <rev>^-<n>. See SPECIFYING RANGES in
37 gitrevisions(7) for more details.
38 • <rev1>...<rev2>. This is equivalent to <rev2>..<rev1>
40 <rev1>..<rev2>.
41 • <base> <rev1> <rev2>: This is equivalent to <base>..<rev1>
43 <base>..<rev2>.
44
46 --no-dual-color
47 When the commit diffs differ, git range-diff recreates the original
48 diffs' coloring, and adds outer -/+ diff markers with the
49 background being red/green to make it easier to see e.g. when there
50 was a change in what exact lines were added.
51 Additionally, the commit diff lines that are only present in the
53 first commit range are shown "dimmed" (this can be overridden using
54 the color.diff.<slot> config setting where <slot> is one of
55 contextDimmed, oldDimmed and newDimmed), and the commit diff lines
56 that are only present in the second commit range are shown in bold
57 (which can be overridden using the config settings
58 color.diff.<slot> with <slot> being one of contextBold, oldBold or
59 newBold).
60 This is known to range-diff as "dual coloring". Use --no-dual-color
62 to revert to color all lines according to the outer diff markers
63 (and completely ignore the inner diff when it comes to color).
64 --creation-factor=<percent>
66 Set the creation/deletion cost fudge factor to <percent>. Defaults
67 to 60. Try a larger value if git range-diff erroneously considers a
68 large change a total rewrite (deletion of one commit and addition
69 of another), and a smaller one in the reverse case. See the
70 ``Algorithm`` section below for an explanation why this is needed.
71 --left-only
73 Suppress commits that are missing from the first specified range
74 (or the "left range" when using the <rev1>...<rev2> format).
75 --right-only
77 Suppress commits that are missing from the second specified range
78 (or the "right range" when using the <rev1>...<rev2> format).
79 --[no-]notes[=<ref>]
81 This flag is passed to the git log program (see git-log(1)) that
82 generates the patches.
83 <range1> <range2>
85 Compare the commits specified by the two ranges, where <range1> is
86 considered an older version of <range2>.
87 <rev1>...<rev2>
89 Equivalent to passing <rev2>..<rev1> and <rev1>..<rev2>.
90 <base> <rev1> <rev2>
92 Equivalent to passing <base>..<rev1> and <base>..<rev2>. Note that
93 <base> does not need to be the exact branch point of the branches.
94 Example: after rebasing a branch my-topic, git range-diff
95 my-topic@{u} my-topic@{1} my-topic would show the differences
96 introduced by the rebase.
97 git range-diff also accepts the regular diff options (see git-diff(1)),
99 most notably the --color=[<when>] and --no-color options. These options
100 are used when generating the "diff between patches", i.e. to compare
101 the author, commit message and diff of corresponding old/new commits.
102 There is currently no means to tweak most of the diff options passed to
103 git log when generating those patches.
104
106 The output of the range-diff command is subject to change. It is
107 intended to be human-readable porcelain output, not something that can
108 be used across versions of Git to get a textually stable range-diff (as
109 opposed to something like the --stable option to git-patch-id(1)).
110 There’s also no equivalent of git-apply(1) for range-diff, the output
111 is not intended to be machine-readable.
112 This is particularly true when passing in diff options. Currently some
114 options like --stat can, as an emergent effect, produce output that’s
115 quite useless in the context of range-diff. Future versions of
116 range-diff may learn to interpret such options in a manner specific to
117 range-diff (e.g. for --stat producing human-readable output which
118 summarizes how the diffstat changed).
119
121 This command uses the diff.color.* and pager.range-diff settings (the
122 latter is on by default). See git-config(1).
123
125 When a rebase required merge conflicts to be resolved, compare the
126 changes introduced by the rebase directly afterwards using:
127 $ git range-diff @{u} @{1} @
129 A typical output of git range-diff would look like this:
131 -: ------- > 1: 0ddba11 Prepare for the inevitable!
133 1: c0debee = 2: cab005e Add a helpful message at the start
134 2: f00dbal ! 3: decafe1 Describe a bug
135 @@ -1,3 +1,3 @@
136 Author: A U Thor <author@example.com>
137 -TODO: Describe a bug
139 +Describe a bug
140 @@ -324,5 +324,6
141 This is expected.
142 -+What is unexpected is that it will also crash.
144 ++Unexpectedly, it also crashes. This is a bug, and the jury is
145 ++still out there how to fix it best. See ticket #314 for details.
146 Contact
148 3: bedead < -: ------- TO-UNDO
149 In this example, there are 3 old and 3 new commits, where the developer
151 removed the 3rd, added a new one before the first two, and modified the
152 commit message of the 2nd commit as well its diff.
153 When the output goes to a terminal, it is color-coded by default, just
155 like regular git diff's output. In addition, the first line (adding a
156 commit) is green, the last line (deleting a commit) is red, the second
157 line (with a perfect match) is yellow like the commit header of git
158 show's output, and the third line colors the old commit red, the new
159 one green and the rest like git show's commit header.
160 A naive color-coded diff of diffs is actually a bit hard to read,
162 though, as it colors the entire lines red or green. The line that added
163 "What is unexpected" in the old commit, for example, is completely red,
164 even if the intent of the old commit was to add something.
165 To help with that, range uses the --dual-color mode by default. In this
167 mode, the diff of diffs will retain the original diff colors, and
168 prefix the lines with -/+ markers that have their background red or
169 green, to make it more obvious that they describe how the diff itself
170 changed.
171
173 The general idea is this: we generate a cost matrix between the commits
174 in both commit ranges, then solve the least-cost assignment.
175 The cost matrix is populated thusly: for each pair of commits, both
177 diffs are generated and the "diff of diffs" is generated, with 3
178 context lines, then the number of lines in that diff is used as cost.
179 To avoid false positives (e.g. when a patch has been removed, and an
181 unrelated patch has been added between two iterations of the same patch
182 series), the cost matrix is extended to allow for that, by adding
183 fixed-cost entries for wholesale deletes/adds.
184 Example: Let commits 1--2 be the first iteration of a patch series and
186 A--C the second iteration. Let’s assume that A is a cherry-pick of 2,
187 and C is a cherry-pick of 1 but with a small modification (say, a fixed
188 typo). Visualize the commits as a bipartite graph:
189 1 A
191 2 B
193 C
195 We are looking for a "best" explanation of the new series in terms of
197 the old one. We can represent an "explanation" as an edge in the graph:
198 1 A
200 /
201 2 --------' B
202 C
204 This explanation comes for "free" because there was no change.
206 Similarly C could be explained using 1, but that comes at some cost c>0
207 because of the modification:
208 1 ----. A
210 | /
211 2 ----+---' B
212 |
213 `----- C
214 c>0
215 In mathematical terms, what we are looking for is some sort of a
217 minimum cost bipartite matching; 1 is matched to C at some cost, etc.
218 The underlying graph is in fact a complete bipartite graph; the cost we
219 associate with every edge is the size of the diff between the two
220 commits' patches. To explain also new commits, we introduce dummy nodes
221 on both sides:
222 1 ----. A
224 | /
225 2 ----+---' B
226 |
227 o `----- C
228 c>0
229 o o
230 o o
232 The cost of an edge o--C is the size of C's diff, modified by a fudge
234 factor that should be smaller than 100%. The cost of an edge o--o is
235 free. The fudge factor is necessary because even if 1 and C have
236 nothing in common, they may still share a few empty lines and such,
237 possibly making the assignment 1--C, o--o slightly cheaper than 1--o,
238 o--C even if 1 and C have nothing in common. With the fudge factor we
239 require a much larger common part to consider patches as corresponding.
240 The overall time needed to compute this algorithm is the time needed to
242 compute n+m commit diffs and then n*m diffs of patches, plus the time
243 needed to compute the least-cost assignment between n and m diffs. Git
244 uses an implementation of the Jonker-Volgenant algorithm to solve the
245 assignment problem, which has cubic runtime complexity. The matching
246 found in this case will look like this:
247 1 ----. A
249 | /
250 2 ----+---' B
251 .--+-----'
252 o -' `----- C
253 c>0
254 o ---------- o
255 o ---------- o
257
259 git-log(1)
260
262 Part of the git(1) suite
263Git 2.39.1 2023-01-13 GIT-RANGE-DIFF(1)