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Raw output format

The raw output format from "git-diff-index", "git-diff-tree", "git-diff-files" and "git diff --raw" are very similar.

These commands all compare two sets of things; what is compared differs:

git-diff-index <tree-ish>

compares the <tree-ish> and the files on the filesystem.

git-diff-index --cached <tree-ish>

compares the <tree-ish> and the index.

git-diff-tree [-r] <tree-ish-1> <tree-ish-2> [<pattern>…​]

compares the trees named by the two arguments.

git-diff-files [<pattern>…​]

compares the index and the files on the filesystem.

The "git-diff-tree" command begins its output by printing the hash of what is being compared. After that, all the commands print one output line per changed file.

An output line is formatted this way:

in-place edit  :100644 100644 bcd1234 0123456 M file0
copy-edit      :100644 100644 abcd123 1234567 C68 file1 file2
rename-edit    :100644 100644 abcd123 1234567 R86 file1 file3
create         :000000 100644 0000000 1234567 A file4
delete         :100644 000000 1234567 0000000 D file5
unmerged       :000000 000000 0000000 0000000 U file6

That is, from the left to the right:

  1. a colon.

  2. mode for "src"; 000000 if creation or unmerged.

  3. a space.

  4. mode for "dst"; 000000 if deletion or unmerged.

  5. a space.

  6. sha1 for "src"; 0{40} if creation or unmerged.

  7. a space.

  8. sha1 for "dst"; 0{40} if deletion, unmerged or "work tree out of sync with the index".

  9. a space.

  10. status, followed by optional "score" number.

  11. a tab or a NUL when -z option is used.

  12. path for "src"

  13. a tab or a NUL when -z option is used; only exists for C or R.

  14. path for "dst"; only exists for C or R.

  15. an LF or a NUL when -z option is used, to terminate the record.

Possible status letters are:

  • A: addition of a file

  • C: copy of a file into a new one

  • D: deletion of a file

  • M: modification of the contents or mode of a file

  • R: renaming of a file

  • T: change in the type of the file (regular file, symbolic link or submodule)

  • U: file is unmerged (you must complete the merge before it can be committed)

  • X: "unknown" change type (most probably a bug, please report it)

Status letters C and R are always followed by a score (denoting the percentage of similarity between the source and target of the move or copy). Status letter M may be followed by a score (denoting the percentage of dissimilarity) for file rewrites.

The sha1 for "dst" is shown as all 0’s if a file on the filesystem is out of sync with the index.

Example:

:100644 100644 5be4a4a 0000000 M file.c

Without the -z option, pathnames with "unusual" characters are quoted as explained for the configuration variable core.quotePath (see git-config[1]). Using -z the filename is output verbatim and the line is terminated by a NUL byte.

diff format for merges

"git-diff-tree", "git-diff-files" and "git-diff --raw" can take -c or --cc option to generate diff output also for merge commits. The output differs from the format described above in the following way:

  1. there is a colon for each parent

  2. there are more "src" modes and "src" sha1

  3. status is concatenated status characters for each parent

  4. no optional "score" number

  5. tab-separated pathname(s) of the file

For -c and --cc, only the destination or final path is shown even if the file was renamed on any side of history. With --combined-all-paths, the name of the path in each parent is shown followed by the name of the path in the merge commit.

Examples for -c and --cc without --combined-all-paths:

::100644 100644 100644 fabadb8 cc95eb0 4866510 MM	desc.c
::100755 100755 100755 52b7a2d 6d1ac04 d2ac7d7 RM	bar.sh
::100644 100644 100644 e07d6c5 9042e82 ee91881 RR	phooey.c

Examples when --combined-all-paths added to either -c or --cc:

::100644 100644 100644 fabadb8 cc95eb0 4866510 MM	desc.c	desc.c	desc.c
::100755 100755 100755 52b7a2d 6d1ac04 d2ac7d7 RM	foo.sh	bar.sh	bar.sh
::100644 100644 100644 e07d6c5 9042e82 ee91881 RR	fooey.c	fuey.c	phooey.c

Note that combined diff lists only files which were modified from all parents.

Generating patch text with -p

Running git-diff[1], git-log[1], git-show[1], git-diff-index[1], git-diff-tree[1], or git-diff-files[1] with the -p option produces patch text. You can customize the creation of patch text via the GIT_EXTERNAL_DIFF and the GIT_DIFF_OPTS environment variables (see git[1]), and the diff attribute (see gitattributes[5]).

What the -p option produces is slightly different from the traditional diff format:

  1. It is preceded by 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 a 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 the 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 blob object names 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. Pathnames with "unusual" characters are quoted as explained for the configuration variable core.quotePath (see git-config[1]).

  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

  5. Hunk headers mention the name of the function to which the hunk applies. See "Defining a custom hunk-header" in gitattributes[5] for details of how to tailor this to specific languages.

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 git-diff[1] or git-show[1]. Note also that you can give suitable --diff-merges option to any of these commands to force generation of diffs in a specific format.

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 by a "git diff" header, that looks like this (when the -c option is used):

    diff --combined file

    or like this (when the --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 content movement (renames and copying detection) are designed to work with the diff of two <tree-ish> and are not used by combined diff format.

  3. It is followed by a two-line from-file/to-file header:

    --- a/file
+++ b/file

    Similar to the two-line header for the traditional unified diff format, /dev/null is used to signal created or deleted files.

    However, if the --combined-all-paths option is provided, instead of a two-line from-file/to-file, you get an N+1 line from-file/to-file header, where N is the number of parents in the merge commit:

    --- a/file
--- a/file
--- a/file
+++ b/file

    This extended format can be useful if rename or copy detection is active, to allow you to see the original name of the file in different parents.

  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 to be applied. 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 or 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").

other diff formats

The --summary option describes newly added, deleted, renamed and copied files. The --stat option adds diffstat(1) graph to the output. These options can be combined with other options, such as -p, and are meant for human consumption.

When showing a change that involves a rename or a copy, --stat output formats the pathnames compactly by combining common prefix and suffix of the pathnames. For example, a change that moves arch/i386/Makefile to arch/x86/Makefile while modifying 4 lines will be shown like this:

arch/{i386 => x86}/Makefile    |   4 +--

The --numstat option gives the diffstat(1) information but is designed for easier machine consumption. An entry in --numstat output looks like this:

1	2	README
3	1	arch/{i386 => x86}/Makefile

That is, from left to right:

  1. the number of added lines;

  2. a tab;

  3. the number of deleted lines;

  4. a tab;

  5. pathname (possibly with rename/copy information);

  6. a newline.

When -z output option is in effect, the output is formatted this way:

1	2	README NUL
3	1	NUL arch/i386/Makefile NUL arch/x86/Makefile NUL

That is:

  1. the number of added lines;

  2. a tab;

  3. the number of deleted lines;

  4. a tab;

  5. a NUL (only exists if renamed/copied);

  6. pathname in preimage;

  7. a NUL (only exists if renamed/copied);

  8. pathname in postimage (only exists if renamed/copied);

  9. a NUL.

The extra NUL before the preimage path in renamed case is to allow scripts that read the output to tell if the current record being read is a single-path record or a rename/copy record without reading ahead. After reading added and deleted lines, reading up to NUL would yield the pathname, but if that is NUL, the record will show two paths.

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