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272bd3cf MV |
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 | |
88d9d45d PB |
59 | with "git log -p", this is the default format; you can force showing |
60 | full diff with the '-m' option. | |
272bd3cf MV |
61 | A 'combined diff' format looks like this: |
62 | ||
63 | ------------ | |
64 | diff --combined describe.c | |
65 | index fabadb8,cc95eb0..4866510 | |
66 | --- a/describe.c | |
67 | +++ b/describe.c | |
68 | @@@ -98,20 -98,12 +98,20 @@@ | |
69 | return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1; | |
70 | } | |
71 | ||
72 | - static void describe(char *arg) | |
73 | -static void describe(struct commit *cmit, int last_one) | |
74 | ++static void describe(char *arg, int last_one) | |
75 | { | |
76 | + unsigned char sha1[20]; | |
77 | + struct commit *cmit; | |
78 | struct commit_list *list; | |
79 | static int initialized = 0; | |
80 | struct commit_name *n; | |
81 | ||
82 | + if (get_sha1(arg, sha1) < 0) | |
83 | + usage(describe_usage); | |
84 | + cmit = lookup_commit_reference(sha1); | |
85 | + if (!cmit) | |
86 | + usage(describe_usage); | |
87 | + | |
88 | if (!initialized) { | |
89 | initialized = 1; | |
90 | for_each_ref(get_name); | |
91 | ------------ | |
92 | ||
93 | 1. It is preceded with a "git diff" header, that looks like | |
94 | this (when '-c' option is used): | |
95 | ||
96 | diff --combined file | |
97 | + | |
98 | or like this (when '--cc' option is used): | |
99 | ||
e57c817d | 100 | diff --cc file |
272bd3cf MV |
101 | |
102 | 2. It is followed by one or more extended header lines | |
103 | (this example shows a merge with two parents): | |
104 | ||
105 | index <hash>,<hash>..<hash> | |
106 | mode <mode>,<mode>..<mode> | |
107 | new file mode <mode> | |
108 | deleted file mode <mode>,<mode> | |
109 | + | |
110 | The `mode <mode>,<mode>..<mode>` line appears only if at least one of | |
111 | the <mode> is different from the rest. Extended headers with | |
112 | information about detected contents movement (renames and | |
113 | copying detection) are designed to work with diff of two | |
114 | <tree-ish> and are not used by combined diff format. | |
115 | ||
116 | 3. It is followed by two-line from-file/to-file header | |
117 | ||
118 | --- a/file | |
119 | +++ b/file | |
120 | + | |
121 | Similar to two-line header for traditional 'unified' diff | |
122 | format, `/dev/null` is used to signal created or deleted | |
123 | files. | |
124 | ||
125 | 4. Chunk header format is modified to prevent people from | |
126 | accidentally feeding it to `patch -p1`. Combined diff format | |
127 | was created for review of merge commit changes, and was not | |
128 | meant for apply. The change is similar to the change in the | |
129 | extended 'index' header: | |
130 | ||
131 | @@@ <from-file-range> <from-file-range> <to-file-range> @@@ | |
132 | + | |
133 | There are (number of parents + 1) `@` characters in the chunk | |
134 | header for combined diff format. | |
135 | ||
136 | Unlike the traditional 'unified' diff format, which shows two | |
137 | files A and B with a single column that has `-` (minus -- | |
138 | appears in A but removed in B), `+` (plus -- missing in A but | |
139 | added to B), or `" "` (space -- unchanged) prefix, this format | |
140 | compares two or more files file1, file2,... with one file X, and | |
141 | shows how X differs from each of fileN. One column for each of | |
142 | fileN is prepended to the output line to note how X's line is | |
143 | different from it. | |
144 | ||
145 | A `-` character in the column N means that the line appears in | |
146 | fileN but it does not appear in the result. A `+` character | |
04c8ce9c | 147 | in the column N means that the line appears in the result, |
272bd3cf MV |
148 | and fileN does not have that line (in other words, the line was |
149 | added, from the point of view of that parent). | |
150 | ||
151 | In the above example output, the function signature was changed | |
152 | from both files (hence two `-` removals from both file1 and | |
153 | file2, plus `++` to mean one line that was added does not appear | |
04c8ce9c MH |
154 | in either file1 nor file2). Also eight other lines are the same |
155 | from file1 but do not appear in file2 (hence prefixed with `{plus}`). | |
272bd3cf MV |
156 | |
157 | When shown by `git diff-tree -c`, it compares the parents of a | |
158 | merge commit with the merge result (i.e. file1..fileN are the | |
159 | parents). When shown by `git diff-files -c`, it compares the | |
160 | two unresolved merge parents with the working tree file | |
161 | (i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka | |
162 | "their version"). |