Edit File: diff-generate-patch.txt
Generating patches with -p -------------------------- When "git-diff-index", "git-diff-tree", or "git-diff-files" are run with a '-p' option, "git diff" without the '--raw' option, or "git log" with the "-p" option, they do not produce the output described above; instead they produce a patch file. You can customize the creation of such patches via the GIT_EXTERNAL_DIFF and the GIT_DIFF_OPTS environment variables. What the -p option produces is slightly different from the traditional diff format: 1. It is preceded with a "git diff" header that looks like this: diff --git a/file1 b/file2 + The `a/` and `b/` filenames are the same unless rename/copy is involved. Especially, even for a creation or a deletion, `/dev/null` is _not_ used in place of the `a/` or `b/` filenames. + When rename/copy is involved, `file1` and `file2` show the name of the source file of the rename/copy and the name of the file that rename/copy produces, respectively. 2. It is followed by one or more extended header lines: old mode <mode> new mode <mode> deleted file mode <mode> new file mode <mode> copy from <path> copy to <path> rename from <path> rename to <path> similarity index <number> dissimilarity index <number> index <hash>..<hash> <mode> + File modes are printed as 6-digit octal numbers including the file type and file permission bits. + Path names in extended headers do not include the `a/` and `b/` prefixes. + The similarity index is the percentage of unchanged lines, and the dissimilarity index is the percentage of changed lines. It is a rounded down integer, followed by a percent sign. The similarity index value of 100% is thus reserved for two equal files, while 100% dissimilarity means that no line from the old file made it into the new one. + The index line includes the SHA-1 checksum before and after the change. The <mode> is included if the file mode does not change; otherwise, separate lines indicate the old and the new mode. 3. TAB, LF, double quote and backslash characters in pathnames are represented as `\t`, `\n`, `\"` and `\\`, respectively. If there is need for such substitution then the whole pathname is put in double quotes. 4. All the `file1` files in the output refer to files before the commit, and all the `file2` files refer to files after the commit. It is incorrect to apply each change to each file sequentially. For example, this patch will swap a and b: diff --git a/a b/b rename from a rename to b diff --git a/b b/a rename from b rename to a combined diff format -------------------- Any diff-generating command can take the `-c` or `--cc` option to produce a 'combined diff' when showing a merge. This is the default format when showing merges with linkgit:git-diff[1] or linkgit:git-show[1]. Note also that you can give the `-m' option to any of these commands to force generation of diffs with individual parents of a merge. A 'combined diff' format looks like this: ------------ diff --combined describe.c index fabadb8,cc95eb0..4866510 --- a/describe.c +++ b/describe.c @@@ -98,20 -98,12 +98,20 @@@ return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1; } - static void describe(char *arg) -static void describe(struct commit *cmit, int last_one) ++static void describe(char *arg, int last_one) { + unsigned char sha1[20]; + struct commit *cmit; struct commit_list *list; static int initialized = 0; struct commit_name *n; + if (get_sha1(arg, sha1) < 0) + usage(describe_usage); + cmit = lookup_commit_reference(sha1); + if (!cmit) + usage(describe_usage); + if (!initialized) { initialized = 1; for_each_ref(get_name); ------------ 1. It is preceded with a "git diff" header, that looks like this (when '-c' option is used): diff --combined file + or like this (when '--cc' option is used): diff --cc file 2. It is followed by one or more extended header lines (this example shows a merge with two parents): index <hash>,<hash>..<hash> mode <mode>,<mode>..<mode> new file mode <mode> deleted file mode <mode>,<mode> + The `mode <mode>,<mode>..<mode>` line appears only if at least one of the <mode> is different from the rest. Extended headers with information about detected contents movement (renames and copying detection) are designed to work with diff of two <tree-ish> and are not used by combined diff format. 3. It is followed by two-line from-file/to-file header --- a/file +++ b/file + Similar to two-line header for traditional 'unified' diff format, `/dev/null` is used to signal created or deleted files. 4. Chunk header format is modified to prevent people from accidentally feeding it to `patch -p1`. Combined diff format was created for review of merge commit changes, and was not meant for apply. The change is similar to the change in the extended 'index' header: @@@ <from-file-range> <from-file-range> <to-file-range> @@@ + There are (number of parents + 1) `@` characters in the chunk header for combined diff format. Unlike the traditional 'unified' diff format, which shows two files A and B with a single column that has `-` (minus -- appears in A but removed in B), `+` (plus -- missing in A but added to B), or `" "` (space -- unchanged) prefix, this format compares two or more files file1, file2,... with one file X, and shows how X differs from each of fileN. One column for each of fileN is prepended to the output line to note how X's line is different from it. A `-` character in the column N means that the line appears in fileN but it does not appear in the result. A `+` character in the column N means that the line appears in the result, and fileN does not have that line (in other words, the line was added, from the point of view of that parent). In the above example output, the function signature was changed from both files (hence two `-` removals from both file1 and file2, plus `++` to mean one line that was added does not appear in either file1 nor file2). Also eight other lines are the same from file1 but do not appear in file2 (hence prefixed with `+`). When shown by `git diff-tree -c`, it compares the parents of a merge commit with the merge result (i.e. file1..fileN are the parents). When shown by `git diff-files -c`, it compares the two unresolved merge parents with the working tree file (i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka "their version").