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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 | |
47d81b5c | 9 | `GIT_EXTERNAL_DIFF` and the `GIT_DIFF_OPTS` environment variables. |
272bd3cf MV |
10 | |
11 | What the -p option produces is slightly different from the traditional | |
9659df52 | 12 | diff format: |
272bd3cf | 13 | |
9659df52 | 14 | 1. It is preceded with a "git diff" header that looks like this: |
272bd3cf MV |
15 | |
16 | diff --git a/file1 b/file2 | |
17 | + | |
18 | The `a/` and `b/` filenames are the same unless rename/copy is | |
19 | involved. Especially, even for a creation or a deletion, | |
9659df52 | 20 | `/dev/null` is _not_ used in place of the `a/` or `b/` filenames. |
272bd3cf MV |
21 | + |
22 | When rename/copy is involved, `file1` and `file2` show the | |
23 | name of the source file of the rename/copy and the name of | |
24 | the file that rename/copy produces, respectively. | |
25 | ||
26 | 2. It is followed by one or more extended header lines: | |
27 | ||
28 | old mode <mode> | |
29 | new mode <mode> | |
30 | deleted file mode <mode> | |
31 | new file mode <mode> | |
32 | copy from <path> | |
33 | copy to <path> | |
34 | rename from <path> | |
35 | rename to <path> | |
36 | similarity index <number> | |
37 | dissimilarity index <number> | |
38 | index <hash>..<hash> <mode> | |
9659df52 AG |
39 | + |
40 | File modes are printed as 6-digit octal numbers including the file type | |
41 | and file permission bits. | |
42 | + | |
43 | Path names in extended headers do not include the `a/` and `b/` prefixes. | |
44 | + | |
272bd3cf MV |
45 | The similarity index is the percentage of unchanged lines, and |
46 | the dissimilarity index is the percentage of changed lines. It | |
47 | is a rounded down integer, followed by a percent sign. The | |
48 | similarity index value of 100% is thus reserved for two equal | |
49 | files, while 100% dissimilarity means that no line from the old | |
50 | file made it into the new one. | |
9659df52 AG |
51 | + |
52 | The index line includes the SHA-1 checksum before and after the change. | |
53 | The <mode> is included if the file mode does not change; otherwise, | |
54 | separate lines indicate the old and the new mode. | |
55 | ||
56 | 3. TAB, LF, double quote and backslash characters in pathnames | |
57 | are represented as `\t`, `\n`, `\"` and `\\`, respectively. | |
58 | If there is need for such substitution then the whole | |
59 | pathname is put in double quotes. | |
60 | ||
61 | 4. All the `file1` files in the output refer to files before the | |
62 | commit, and all the `file2` files refer to files after the commit. | |
63 | It is incorrect to apply each change to each file sequentially. For | |
64 | example, this patch will swap a and b: | |
65 | ||
66 | diff --git a/a b/b | |
67 | rename from a | |
68 | rename to b | |
69 | diff --git a/b b/a | |
70 | rename from b | |
71 | rename to a | |
272bd3cf MV |
72 | |
73 | ||
74 | combined diff format | |
75 | -------------------- | |
76 | ||
e0adb84c AM |
77 | Any diff-generating command can take the `-c` or `--cc` option to |
78 | produce a 'combined diff' when showing a merge. This is the default | |
79 | format when showing merges with linkgit:git-diff[1] or | |
e08bc7a9 | 80 | linkgit:git-show[1]. Note also that you can give the `-m` option to any |
e0adb84c AM |
81 | of these commands to force generation of diffs with individual parents |
82 | of a merge. | |
83 | ||
272bd3cf MV |
84 | A 'combined diff' format looks like this: |
85 | ||
86 | ------------ | |
87 | diff --combined describe.c | |
88 | index fabadb8,cc95eb0..4866510 | |
89 | --- a/describe.c | |
90 | +++ b/describe.c | |
91 | @@@ -98,20 -98,12 +98,20 @@@ | |
92 | return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1; | |
93 | } | |
94 | ||
95 | - static void describe(char *arg) | |
96 | -static void describe(struct commit *cmit, int last_one) | |
97 | ++static void describe(char *arg, int last_one) | |
98 | { | |
99 | + unsigned char sha1[20]; | |
100 | + struct commit *cmit; | |
101 | struct commit_list *list; | |
102 | static int initialized = 0; | |
103 | struct commit_name *n; | |
104 | ||
105 | + if (get_sha1(arg, sha1) < 0) | |
106 | + usage(describe_usage); | |
107 | + cmit = lookup_commit_reference(sha1); | |
108 | + if (!cmit) | |
109 | + usage(describe_usage); | |
110 | + | |
111 | if (!initialized) { | |
112 | initialized = 1; | |
113 | for_each_ref(get_name); | |
114 | ------------ | |
115 | ||
116 | 1. It is preceded with a "git diff" header, that looks like | |
117 | this (when '-c' option is used): | |
118 | ||
119 | diff --combined file | |
120 | + | |
121 | or like this (when '--cc' option is used): | |
122 | ||
e57c817d | 123 | diff --cc file |
272bd3cf MV |
124 | |
125 | 2. It is followed by one or more extended header lines | |
126 | (this example shows a merge with two parents): | |
127 | ||
128 | index <hash>,<hash>..<hash> | |
129 | mode <mode>,<mode>..<mode> | |
130 | new file mode <mode> | |
131 | deleted file mode <mode>,<mode> | |
132 | + | |
133 | The `mode <mode>,<mode>..<mode>` line appears only if at least one of | |
134 | the <mode> is different from the rest. Extended headers with | |
135 | information about detected contents movement (renames and | |
136 | copying detection) are designed to work with diff of two | |
137 | <tree-ish> and are not used by combined diff format. | |
138 | ||
139 | 3. It is followed by two-line from-file/to-file header | |
140 | ||
141 | --- a/file | |
142 | +++ b/file | |
143 | + | |
144 | Similar to two-line header for traditional 'unified' diff | |
145 | format, `/dev/null` is used to signal created or deleted | |
146 | files. | |
147 | ||
148 | 4. Chunk header format is modified to prevent people from | |
149 | accidentally feeding it to `patch -p1`. Combined diff format | |
150 | was created for review of merge commit changes, and was not | |
151 | meant for apply. The change is similar to the change in the | |
152 | extended 'index' header: | |
153 | ||
154 | @@@ <from-file-range> <from-file-range> <to-file-range> @@@ | |
155 | + | |
156 | There are (number of parents + 1) `@` characters in the chunk | |
157 | header for combined diff format. | |
158 | ||
159 | Unlike the traditional 'unified' diff format, which shows two | |
160 | files A and B with a single column that has `-` (minus -- | |
161 | appears in A but removed in B), `+` (plus -- missing in A but | |
162 | added to B), or `" "` (space -- unchanged) prefix, this format | |
163 | compares two or more files file1, file2,... with one file X, and | |
164 | shows how X differs from each of fileN. One column for each of | |
165 | fileN is prepended to the output line to note how X's line is | |
166 | different from it. | |
167 | ||
168 | A `-` character in the column N means that the line appears in | |
169 | fileN but it does not appear in the result. A `+` character | |
04c8ce9c | 170 | in the column N means that the line appears in the result, |
272bd3cf MV |
171 | and fileN does not have that line (in other words, the line was |
172 | added, from the point of view of that parent). | |
173 | ||
174 | In the above example output, the function signature was changed | |
175 | from both files (hence two `-` removals from both file1 and | |
176 | file2, plus `++` to mean one line that was added does not appear | |
a58088ab | 177 | in either file1 or file2). Also eight other lines are the same |
6cf378f0 | 178 | from file1 but do not appear in file2 (hence prefixed with `+`). |
272bd3cf MV |
179 | |
180 | When shown by `git diff-tree -c`, it compares the parents of a | |
181 | merge commit with the merge result (i.e. file1..fileN are the | |
182 | parents). When shown by `git diff-files -c`, it compares the | |
183 | two unresolved merge parents with the working tree file | |
184 | (i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka | |
185 | "their version"). |