git/Documentation/diff-format.txt

The 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.


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:

. a colon.
. mode for "src"; 000000 if creation or unmerged.
. a space.
. mode for "dst"; 000000 if deletion or unmerged.
. a space.
. sha1 for "src"; 0\{40\} if creation or unmerged.
. a space.
. sha1 for "dst"; 0\{40\} if creation, unmerged or "look at work tree".
. a space.
. status, followed by optional "score" number.
. a tab or a NUL when '-z' option is used.
. path for "src"
. a tab or a NUL when '-z' option is used; only exists for C or R.
. path for "dst"; only exists for C or R.
. 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
- 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), and are the only ones to be so.

<sha1> is shown as all 0's if a file is new on the filesystem
and it is out of sync with the index.

Example:

------------------------------------------------
:100644 100644 5be4a4...... 000000...... M file.c
------------------------------------------------

When `-z` option is not used, TAB, LF, and backslash characters
in pathnames are represented as `\t`, `\n`, and `\\`,
respectively.

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:

. there is a colon for each parent
. there are more "src" modes and "src" sha1
. status is concatenated status characters for each parent
. no optional "score" number
. single path, only for "dst"

Example:

------------------------------------------------
::100644 100644 100644 fabadb8... cc95eb0... 4866510... MM	describe.c
------------------------------------------------

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


include::diff-generate-patch.txt[]


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:

. the number of added lines;
. a tab;
. the number of deleted lines;
. a tab;
. pathname (possibly with rename/copy information);
. 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:

. the number of added lines;
. a tab;
. the number of deleted lines;
. a tab;
. a NUL (only exists if renamed/copied);
. pathname in preimage;
. a NUL (only exists if renamed/copied);
. pathname in postimage (only exists if renamed/copied);
. 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.