diff, log doc: small grammer, format, and language fixes
[git/git.git] / Documentation / diff-generate-patch.txt
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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
47d81b5c 13`GIT_EXTERNAL_DIFF` and the `GIT_DIFF_OPTS` environment variables.
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14
15What the -p option produces is slightly different from the traditional
9659df52 16diff format:
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9659df52 181. It is preceded with a "git diff" header that looks like this:
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19
20 diff --git a/file1 b/file2
21+
22The `a/` and `b/` filenames are the same unless rename/copy is
23involved. Especially, even for a creation or a deletion,
9659df52 24`/dev/null` is _not_ used in place of the `a/` or `b/` filenames.
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25+
26When rename/copy is involved, `file1` and `file2` show the
27name of the source file of the rename/copy and the name of
28the file that rename/copy produces, respectively.
29
302. It is followed by one or more extended header lines:
31
32 old mode <mode>
33 new mode <mode>
34 deleted file mode <mode>
35 new file mode <mode>
36 copy from <path>
37 copy to <path>
38 rename from <path>
39 rename to <path>
40 similarity index <number>
41 dissimilarity index <number>
42 index <hash>..<hash> <mode>
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43+
44File modes are printed as 6-digit octal numbers including the file type
45and file permission bits.
46+
47Path names in extended headers do not include the `a/` and `b/` prefixes.
48+
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49The similarity index is the percentage of unchanged lines, and
50the dissimilarity index is the percentage of changed lines. It
51is a rounded down integer, followed by a percent sign. The
52similarity index value of 100% is thus reserved for two equal
53files, while 100% dissimilarity means that no line from the old
54file made it into the new one.
9659df52 55+
0eb7c37a 56The index line includes the blob object names before and after the change.
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57The <mode> is included if the file mode does not change; otherwise,
58separate lines indicate the old and the new mode.
59
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603. Pathnames with "unusual" characters are quoted as explained for
61 the configuration variable `core.quotePath` (see
62 linkgit:git-config[1]).
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63
644. All the `file1` files in the output refer to files before the
65 commit, and all the `file2` files refer to files after the commit.
66 It is incorrect to apply each change to each file sequentially. For
67 example, this patch will swap a and b:
68
69 diff --git a/a b/b
70 rename from a
71 rename to b
72 diff --git a/b b/a
73 rename from b
74 rename to a
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75
76
0eb7c37a 77Combined diff format
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78--------------------
79
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80Any diff-generating command can take the `-c` or `--cc` option to
81produce a 'combined diff' when showing a merge. This is the default
82format when showing merges with linkgit:git-diff[1] or
e08bc7a9 83linkgit:git-show[1]. Note also that you can give the `-m` option to any
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84of these commands to force generation of diffs with individual parents
85of a merge.
86
0eb7c37a 87A "combined diff" format looks like this:
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88
89------------
90diff --combined describe.c
91index fabadb8,cc95eb0..4866510
92--- a/describe.c
93+++ b/describe.c
94@@@ -98,20 -98,12 +98,20 @@@
95 return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
96 }
97
98- static void describe(char *arg)
99 -static void describe(struct commit *cmit, int last_one)
100++static void describe(char *arg, int last_one)
101 {
102 + unsigned char sha1[20];
103 + struct commit *cmit;
104 struct commit_list *list;
105 static int initialized = 0;
106 struct commit_name *n;
107
108 + if (get_sha1(arg, sha1) < 0)
109 + usage(describe_usage);
110 + cmit = lookup_commit_reference(sha1);
111 + if (!cmit)
112 + usage(describe_usage);
113 +
114 if (!initialized) {
115 initialized = 1;
116 for_each_ref(get_name);
117------------
118
1191. It is preceded with a "git diff" header, that looks like
0eb7c37a 120 this (when the `-c` option is used):
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121
122 diff --combined file
123+
0eb7c37a 124or like this (when the `--cc` option is used):
272bd3cf 125
e57c817d 126 diff --cc file
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127
1282. It is followed by one or more extended header lines
129 (this example shows a merge with two parents):
130
131 index <hash>,<hash>..<hash>
132 mode <mode>,<mode>..<mode>
133 new file mode <mode>
134 deleted file mode <mode>,<mode>
135+
136The `mode <mode>,<mode>..<mode>` line appears only if at least one of
137the <mode> is different from the rest. Extended headers with
138information about detected contents movement (renames and
139copying detection) are designed to work with diff of two
140<tree-ish> and are not used by combined diff format.
141
1423. It is followed by two-line from-file/to-file header
143
144 --- a/file
145 +++ b/file
146+
147Similar to two-line header for traditional 'unified' diff
148format, `/dev/null` is used to signal created or deleted
149files.
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150+
151However, if the --combined-all-paths option is provided, instead of a
152two-line from-file/to-file you get a N+1 line from-file/to-file header,
153where N is the number of parents in the merge commit
154
155 --- a/file
156 --- a/file
157 --- a/file
158 +++ b/file
159+
160This extended format can be useful if rename or copy detection is
161active, to allow you to see the original name of the file in different
162parents.
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163
1644. Chunk header format is modified to prevent people from
165 accidentally feeding it to `patch -p1`. Combined diff format
166 was created for review of merge commit changes, and was not
0eb7c37a 167 meant to be applied. The change is similar to the change in the
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168 extended 'index' header:
169
170 @@@ <from-file-range> <from-file-range> <to-file-range> @@@
171+
172There are (number of parents + 1) `@` characters in the chunk
173header for combined diff format.
174
175Unlike the traditional 'unified' diff format, which shows two
176files A and B with a single column that has `-` (minus --
177appears in A but removed in B), `+` (plus -- missing in A but
178added to B), or `" "` (space -- unchanged) prefix, this format
179compares two or more files file1, file2,... with one file X, and
180shows how X differs from each of fileN. One column for each of
181fileN is prepended to the output line to note how X's line is
182different from it.
183
184A `-` character in the column N means that the line appears in
185fileN but it does not appear in the result. A `+` character
04c8ce9c 186in the column N means that the line appears in the result,
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187and fileN does not have that line (in other words, the line was
188added, from the point of view of that parent).
189
190In the above example output, the function signature was changed
191from both files (hence two `-` removals from both file1 and
192file2, plus `++` to mean one line that was added does not appear
a58088ab 193in either file1 or file2). Also eight other lines are the same
6cf378f0 194from file1 but do not appear in file2 (hence prefixed with `+`).
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195
196When shown by `git diff-tree -c`, it compares the parents of a
197merge commit with the merge result (i.e. file1..fileN are the
198parents). When shown by `git diff-files -c`, it compares the
199two unresolved merge parents with the working tree file
200(i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka
201"their version").