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git/Documentation/diff-format.txt
Junio C Hamano 215a7ad1ef Big tool rename.
As promised, this is the "big tool rename" patch.  The primary differences
since 0.99.6 are:

  (1) git-*-script are no more.  The commands installed do not
      have any such suffix so users do not have to remember if
      something is implemented as a shell script or not.

  (2) Many command names with 'cache' in them are renamed with
      'index' if that is what they mean.

There are backward compatibility symblic links so that you and
Porcelains can keep using the old names, but the backward
compatibility support  is expected to be removed in the near
future.

Signed-off-by: Junio C Hamano <junkio@cox.net>
2005-09-07 17:45:20 -07:00

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The output format from "git-diff-index", "git-diff-tree" and
"git-diff-files" are very similar.
These commands all compare two sets of things; what are
compared are different:
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 cache.
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 cache 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.
<sha1> is shown as all 0's if new is a file on the filesystem
and it is out of sync with the cache.
Example:
------------------------------------------------
:100644 100644 5be4a4...... 000000...... M file.c
------------------------------------------------
Generating patches with -p
--------------------------
When "git-diff-index", "git-diff-tree", or "git-diff-files" are run
with a '-p' option, they do not produce the output described above;
instead they produce a patch file.
The patch generation can be customized at two levels. This
customization also applies to "git-diff-helper".
1. When the environment variable 'GIT_EXTERNAL_DIFF' is not set,
these commands internally invoke "diff" like this:
diff -L a/<path> -L b/<path> -pu <old> <new>
+
For added files, `/dev/null` is used for <old>. For removed
files, `/dev/null` is used for <new>
+
The "diff" formatting options can be customized via the
environment variable 'GIT_DIFF_OPTS'. For example, if you
prefer context diff:
GIT_DIFF_OPTS=-c git-diff-index -p $(cat .git/HEAD)
2. When the environment variable 'GIT_EXTERNAL_DIFF' is set, the
program named by it is called, instead of the diff invocation
described above.
+
For a path that is added, removed, or modified,
'GIT_EXTERNAL_DIFF' is called with 7 parameters:
path old-file old-hex old-mode new-file new-hex new-mode
+
where:
<old|new>-file:: are files GIT_EXTERNAL_DIFF can use to read the
contents of <old|ne>,
<old|new>-hex:: are the 40-hexdigit SHA1 hashes,
<old|new>-mode:: are the octal representation of the file modes.
+
The file parameters can point at the user's working file
(e.g. `new-file` in "git-diff-files"), `/dev/null` (e.g. `old-file`
when a new file is added), or a temporary file (e.g. `old-file` in the
cache). 'GIT_EXTERNAL_DIFF' should not worry about unlinking the
temporary file --- it is removed when 'GIT_EXTERNAL_DIFF' exits.
For a path that is unmerged, 'GIT_EXTERNAL_DIFF' is called with 1
parameter, <path>.
Git specific extension to diff format
-------------------------------------
What -p option produces is slightly different from the
traditional diff format.
1. It is preceeded 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 `a/` or `b/` filenames.
+
When rename/copy is involved, `file1` and `file2` shows 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 extended header lines that are one or
more of:
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>