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1Generating patch text with -p
2-----------------------------
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4Running
5linkgit:git-diff[1],
6linkgit:git-log[1],
7linkgit:git-show[1],
8linkgit:git-diff-index[1],
9linkgit:git-diff-tree[1], or
10linkgit:git-diff-files[1]
11with the `-p` option produces patch text.
12You can customize the creation of patch text via the
17bae894 13`GIT_EXTERNAL_DIFF` and the `GIT_DIFF_OPTS` environment variables
7a14acdb 14(see linkgit:git[1]), and the `diff` attribute (see linkgit:gitattributes[5]).
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15
16What the -p option produces is slightly different from the traditional
9659df52 17diff format:
272bd3cf 18
9659df52 191. It is preceded with a "git diff" header that looks like this:
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20
21 diff --git a/file1 b/file2
22+
23The `a/` and `b/` filenames are the same unless rename/copy is
24involved. Especially, even for a creation or a deletion,
9659df52 25`/dev/null` is _not_ used in place of the `a/` or `b/` filenames.
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26+
27When rename/copy is involved, `file1` and `file2` show the
28name of the source file of the rename/copy and the name of
29the file that rename/copy produces, respectively.
30
312. It is followed by one or more extended header lines:
32
33 old mode <mode>
34 new mode <mode>
35 deleted file mode <mode>
36 new file mode <mode>
37 copy from <path>
38 copy to <path>
39 rename from <path>
40 rename to <path>
41 similarity index <number>
42 dissimilarity index <number>
43 index <hash>..<hash> <mode>
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44+
45File modes are printed as 6-digit octal numbers including the file type
46and file permission bits.
47+
48Path names in extended headers do not include the `a/` and `b/` prefixes.
49+
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50The similarity index is the percentage of unchanged lines, and
51the dissimilarity index is the percentage of changed lines. It
52is a rounded down integer, followed by a percent sign. The
53similarity index value of 100% is thus reserved for two equal
54files, while 100% dissimilarity means that no line from the old
55file made it into the new one.
9659df52 56+
0eb7c37a 57The index line includes the blob object names before and after the change.
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58The <mode> is included if the file mode does not change; otherwise,
59separate lines indicate the old and the new mode.
60
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613. Pathnames with "unusual" characters are quoted as explained for
62 the configuration variable `core.quotePath` (see
63 linkgit:git-config[1]).
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64
654. All the `file1` files in the output refer to files before the
66 commit, and all the `file2` files refer to files after the commit.
67 It is incorrect to apply each change to each file sequentially. For
68 example, this patch will swap a and b:
69
70 diff --git a/a b/b
71 rename from a
72 rename to b
73 diff --git a/b b/a
74 rename from b
75 rename to a
272bd3cf 76
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775. Hunk headers mention the name of the function to which the hunk
78 applies. See "Defining a custom hunk-header" in
79 linkgit:gitattributes[5] for details of how to tailor to this to
80 specific languages.
81
272bd3cf 82
0eb7c37a 83Combined diff format
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84--------------------
85
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86Any diff-generating command can take the `-c` or `--cc` option to
87produce a 'combined diff' when showing a merge. This is the default
88format when showing merges with linkgit:git-diff[1] or
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89linkgit:git-show[1]. Note also that you can give suitable
90`--diff-merges` option to any of these commands to force generation of
91diffs in specific format.
e0adb84c 92
0eb7c37a 93A "combined diff" format looks like this:
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94
95------------
96diff --combined describe.c
97index fabadb8,cc95eb0..4866510
98--- a/describe.c
99+++ b/describe.c
100@@@ -98,20 -98,12 +98,20 @@@
101 return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
102 }
103
104- static void describe(char *arg)
105 -static void describe(struct commit *cmit, int last_one)
106++static void describe(char *arg, int last_one)
107 {
108 + unsigned char sha1[20];
109 + struct commit *cmit;
110 struct commit_list *list;
111 static int initialized = 0;
112 struct commit_name *n;
113
114 + if (get_sha1(arg, sha1) < 0)
115 + usage(describe_usage);
116 + cmit = lookup_commit_reference(sha1);
117 + if (!cmit)
118 + usage(describe_usage);
119 +
120 if (!initialized) {
121 initialized = 1;
122 for_each_ref(get_name);
123------------
124
1251. It is preceded with a "git diff" header, that looks like
0eb7c37a 126 this (when the `-c` option is used):
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127
128 diff --combined file
129+
0eb7c37a 130or like this (when the `--cc` option is used):
272bd3cf 131
e57c817d 132 diff --cc file
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133
1342. It is followed by one or more extended header lines
135 (this example shows a merge with two parents):
136
137 index <hash>,<hash>..<hash>
138 mode <mode>,<mode>..<mode>
139 new file mode <mode>
140 deleted file mode <mode>,<mode>
141+
142The `mode <mode>,<mode>..<mode>` line appears only if at least one of
143the <mode> is different from the rest. Extended headers with
144information about detected contents movement (renames and
145copying detection) are designed to work with diff of two
146<tree-ish> and are not used by combined diff format.
147
1483. It is followed by two-line from-file/to-file header
149
150 --- a/file
151 +++ b/file
152+
153Similar to two-line header for traditional 'unified' diff
154format, `/dev/null` is used to signal created or deleted
155files.
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156+
157However, if the --combined-all-paths option is provided, instead of a
158two-line from-file/to-file you get a N+1 line from-file/to-file header,
159where N is the number of parents in the merge commit
160
161 --- a/file
162 --- a/file
163 --- a/file
164 +++ b/file
165+
166This extended format can be useful if rename or copy detection is
167active, to allow you to see the original name of the file in different
168parents.
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169
1704. Chunk header format is modified to prevent people from
171 accidentally feeding it to `patch -p1`. Combined diff format
172 was created for review of merge commit changes, and was not
0eb7c37a 173 meant to be applied. The change is similar to the change in the
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174 extended 'index' header:
175
176 @@@ <from-file-range> <from-file-range> <to-file-range> @@@
177+
178There are (number of parents + 1) `@` characters in the chunk
179header for combined diff format.
180
181Unlike the traditional 'unified' diff format, which shows two
182files A and B with a single column that has `-` (minus --
183appears in A but removed in B), `+` (plus -- missing in A but
184added to B), or `" "` (space -- unchanged) prefix, this format
185compares two or more files file1, file2,... with one file X, and
186shows how X differs from each of fileN. One column for each of
187fileN is prepended to the output line to note how X's line is
188different from it.
189
190A `-` character in the column N means that the line appears in
191fileN but it does not appear in the result. A `+` character
04c8ce9c 192in the column N means that the line appears in the result,
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193and fileN does not have that line (in other words, the line was
194added, from the point of view of that parent).
195
196In the above example output, the function signature was changed
197from both files (hence two `-` removals from both file1 and
198file2, plus `++` to mean one line that was added does not appear
a58088ab 199in either file1 or file2). Also eight other lines are the same
6cf378f0 200from file1 but do not appear in file2 (hence prefixed with `+`).
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201
202When shown by `git diff-tree -c`, it compares the parents of a
203merge commit with the merge result (i.e. file1..fileN are the
204parents). When shown by `git diff-files -c`, it compares the
205two unresolved merge parents with the working tree file
206(i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka
207"their version").