git-diff-index - Compares content and mode of blobs between the index and repository

git-diff-index [-m] [--cached] [<common diff options>] <tree-ish> [<path>...]

Compares the content and mode of the blobs found via a tree object with the content of the current index and, optionally ignoring the stat state of the file on disk. When paths are specified, compares only those named paths. Otherwise all entries in the index are compared.

-p

Generate patch (see section on generating patches)

-u

Synonym for "-p".

-z

\0 line termination on output

--name-only

Show only names of changed files.

--name-status

Show only names and status of changed files.

--full-index

Instead of the first handful characters, show full object name of pre- and post-image blob on the "index" line when generating a patch format output.

--abbrev[=<n>]

Instead of showing the full 40-byte hexadecimal object name in diff-raw format output and diff-tree header lines, show only handful hexdigits prefix. This is independent of --full-index option above, which controls the diff-patch output format. Non default number of digits can be specified with --abbrev=<n>.

-B

Break complete rewrite changes into pairs of delete and create.

-M

Detect renames.

-C

Detect copies as well as renames.

--find-copies-harder

For performance reasons, by default, -C option finds copies only if the original file of the copy was modified in the same changeset. This flag makes the command inspect unmodified files as candidates for the source of copy. This is a very expensive operation for large projects, so use it with caution.

-l<num>

-M and -C options require O(n^2) processing time where n is the number of potential rename/copy targets. This option prevents rename/copy detection from running if the number of rename/copy targets exceeds the specified number.

-S<string>

Look for differences that contain the change in <string>.

--pickaxe-all

When -S finds a change, show all the changes in that changeset, not just the files that contain the change in <string>.

-O<orderfile>

Output the patch in the order specified in the <orderfile>, which has one shell glob pattern per line.

-R

Swap two inputs; that is, show differences from index or on-disk file to tree contents.

For more detailed explanation on these common options, see also diffcore documentation: diffcore.html.

<tree-ish>

The id of a tree object to diff against.

--cached

do not consider the on-disk file at all

-m

By default, files recorded in the index but not checked out are reported as deleted. This flag makes "git-diff-index" say that all non-checked-out files are up to date.

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 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:

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 creation, unmerged or "look at work tree".

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.

<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.

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.

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 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|new>,

<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 index). 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>.

What -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 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:

3.

TAB, LF, and backslash characters in pathnames are represented as \t, \n, and \\, respectively.

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>

You can choose whether you want to trust the index file entirely (using the --cached flag) or ask the diff logic to show any files that don't match the stat state as being "tentatively changed". Both of these operations are very useful indeed.

If --cached is specified, it allows you to ask:

show me the differences between HEAD and the current index
contents (the ones I'd write with a "git-write-tree")

For example, let's say that you have worked on your working directory, updated some files in the index and are ready to commit. You want to see exactly what you are going to commit is without having to write a new tree object and compare it that way, and to do that, you just do

git-diff-index --cached HEAD

Example: let's say I had renamed commit.c to git-commit.c, and I had done an "git-update-index" to make that effective in the index file. "git-diff-files" wouldn't show anything at all, since the index file matches my working directory. But doing a "git-diff-index" does:

torvalds@ppc970:~/git> git-diff-index --cached HEAD
-100644 blob    4161aecc6700a2eb579e842af0b7f22b98443f74        commit.c
+100644 blob    4161aecc6700a2eb579e842af0b7f22b98443f74        git-commit.c

You can trivially see that the above is a rename.

In fact, "git-diff-index --cached" should always be entirely equivalent to actually doing a "git-write-tree" and comparing that. Except this one is much nicer for the case where you just want to check where you are.

So doing a "git-diff-index --cached" is basically very useful when you are asking yourself "what have I already marked for being committed, and what's the difference to a previous tree".

The "non-cached" mode takes a different approach, and is potentially the more useful of the two in that what it does can't be emulated with a "git-write-tree" + "git-diff-tree". Thus that's the default mode. The non-cached version asks the question:

show me the differences between HEAD and the currently checked out
tree - index contents _and_ files that aren't up-to-date

which is obviously a very useful question too, since that tells you what you could commit. Again, the output matches the "git-diff-tree -r" output to a tee, but with a twist.

The twist is that if some file doesn't match the index, we don't have a backing store thing for it, and we use the magic "all-zero" sha1 to show that. So let's say that you have edited kernel/sched.c, but have not actually done a "git-update-index" on it yet - there is no "object" associated with the new state, and you get:

torvalds@ppc970:~/v2.6/linux> git-diff-index HEAD
*100644->100664 blob    7476bb......->000000......      kernel/sched.c

ie it shows that the tree has changed, and that kernel/sched.c has is not up-to-date and may contain new stuff. The all-zero sha1 means that to get the real diff, you need to look at the object in the working directory directly rather than do an object-to-object diff.

As with other commands of this type, "git-diff-index" does not actually look at the contents of the file at all. So maybe kernel/sched.c hasn't actually changed, and it's just that you touched it. In either case, it's a note that you need to "git-update-index" it to make the index be in sync.

You can have a mixture of files show up as "has been updated" and "is still dirty in the working directory" together. You can always tell which file is in which state, since the "has been updated" ones show a valid sha1, and the "not in sync with the index" ones will always have the special all-zero sha1.

Written by Linus Torvalds <torvalds@osdl.org>

Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>.

Part of the git(7) suite