Include diff options in the git-log manpage
[git/git.git] / Documentation / diff-generate-patch.txt
1 Generating patches with -p
2 --------------------------
3
4 When "git-diff-index", "git-diff-tree", or "git-diff-files" are run
5 with a '-p' option, "git diff" without the '--raw' option, or
6 "git log" with the "-p" option, they
7 do not produce the output described above; instead they produce a
8 patch file. You can customize the creation of such patches via the
9 GIT_EXTERNAL_DIFF and the GIT_DIFF_OPTS environment variables.
10
11 What the -p option produces is slightly different from the traditional
12 diff format.
13
14 1. It is preceded with a "git diff" header, that looks like
15 this:
16
17 diff --git a/file1 b/file2
18 +
19 The `a/` and `b/` filenames are the same unless rename/copy is
20 involved. Especially, even for a creation or a deletion,
21 `/dev/null` is _not_ used in place of `a/` or `b/` filenames.
22 +
23 When rename/copy is involved, `file1` and `file2` show the
24 name of the source file of the rename/copy and the name of
25 the file that rename/copy produces, respectively.
26
27 2. It is followed by one or more extended header lines:
28
29 old mode <mode>
30 new mode <mode>
31 deleted file mode <mode>
32 new file mode <mode>
33 copy from <path>
34 copy to <path>
35 rename from <path>
36 rename to <path>
37 similarity index <number>
38 dissimilarity index <number>
39 index <hash>..<hash> <mode>
40
41 3. TAB, LF, double quote and backslash characters in pathnames
42 are represented as `\t`, `\n`, `\"` and `\\`, respectively.
43 If there is need for such substitution then the whole
44 pathname is put in double quotes.
45
46 The similarity index is the percentage of unchanged lines, and
47 the dissimilarity index is the percentage of changed lines. It
48 is a rounded down integer, followed by a percent sign. The
49 similarity index value of 100% is thus reserved for two equal
50 files, while 100% dissimilarity means that no line from the old
51 file made it into the new one.
52
53
54 combined diff format
55 --------------------
56
57 "git-diff-tree", "git-diff-files" and "git-diff" can take '-c' or
58 '--cc' option to produce 'combined diff'. For showing a merge commit
59 with "git log -p", this is the default format.
60 A 'combined diff' format looks like this:
61
62 ------------
63 diff --combined describe.c
64 index fabadb8,cc95eb0..4866510
65 --- a/describe.c
66 +++ b/describe.c
67 @@@ -98,20 -98,12 +98,20 @@@
68 return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
69 }
70
71 - static void describe(char *arg)
72 -static void describe(struct commit *cmit, int last_one)
73 ++static void describe(char *arg, int last_one)
74 {
75 + unsigned char sha1[20];
76 + struct commit *cmit;
77 struct commit_list *list;
78 static int initialized = 0;
79 struct commit_name *n;
80
81 + if (get_sha1(arg, sha1) < 0)
82 + usage(describe_usage);
83 + cmit = lookup_commit_reference(sha1);
84 + if (!cmit)
85 + usage(describe_usage);
86 +
87 if (!initialized) {
88 initialized = 1;
89 for_each_ref(get_name);
90 ------------
91
92 1. It is preceded with a "git diff" header, that looks like
93 this (when '-c' option is used):
94
95 diff --combined file
96 +
97 or like this (when '--cc' option is used):
98
99 diff --c file
100
101 2. It is followed by one or more extended header lines
102 (this example shows a merge with two parents):
103
104 index <hash>,<hash>..<hash>
105 mode <mode>,<mode>..<mode>
106 new file mode <mode>
107 deleted file mode <mode>,<mode>
108 +
109 The `mode <mode>,<mode>..<mode>` line appears only if at least one of
110 the <mode> is different from the rest. Extended headers with
111 information about detected contents movement (renames and
112 copying detection) are designed to work with diff of two
113 <tree-ish> and are not used by combined diff format.
114
115 3. It is followed by two-line from-file/to-file header
116
117 --- a/file
118 +++ b/file
119 +
120 Similar to two-line header for traditional 'unified' diff
121 format, `/dev/null` is used to signal created or deleted
122 files.
123
124 4. Chunk header format is modified to prevent people from
125 accidentally feeding it to `patch -p1`. Combined diff format
126 was created for review of merge commit changes, and was not
127 meant for apply. The change is similar to the change in the
128 extended 'index' header:
129
130 @@@ <from-file-range> <from-file-range> <to-file-range> @@@
131 +
132 There are (number of parents + 1) `@` characters in the chunk
133 header for combined diff format.
134
135 Unlike the traditional 'unified' diff format, which shows two
136 files A and B with a single column that has `-` (minus --
137 appears in A but removed in B), `+` (plus -- missing in A but
138 added to B), or `" "` (space -- unchanged) prefix, this format
139 compares two or more files file1, file2,... with one file X, and
140 shows how X differs from each of fileN. One column for each of
141 fileN is prepended to the output line to note how X's line is
142 different from it.
143
144 A `-` character in the column N means that the line appears in
145 fileN but it does not appear in the result. A `+` character
146 in the column N means that the line appears in the last file,
147 and fileN does not have that line (in other words, the line was
148 added, from the point of view of that parent).
149
150 In the above example output, the function signature was changed
151 from both files (hence two `-` removals from both file1 and
152 file2, plus `++` to mean one line that was added does not appear
153 in either file1 nor file2). Also two other lines are the same
154 from file1 but do not appear in file2 (hence prefixed with ` +`).
155
156 When shown by `git diff-tree -c`, it compares the parents of a
157 merge commit with the merge result (i.e. file1..fileN are the
158 parents). When shown by `git diff-files -c`, it compares the
159 two unresolved merge parents with the working tree file
160 (i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka
161 "their version").