NAME¶

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

SYNOPSIS¶

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

DESCRIPTION¶

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.

OPTIONS¶

-p, -u

-U<n>, --unified=<n>

--raw

--patch-with-raw

--patience

--stat[=width[,name-width]]

--numstat

--shortstat

--dirstat[=limit]

--dirstat-by-file[=limit]

--summary

--patch-with-stat

-z

--name-only

--name-status

--submodule[=<format>]

--color[=<when>]

--no-color

--color-words[=<regex>]

--no-renames

--check

--full-index

--binary

--abbrev[=<n>]

-B

-M

-C

--diff-filter=[ACDMRTUXB*]

--find-copies-harder

-l<num>

-S<string>

--pickaxe-all

--pickaxe-regex

-O<orderfile>

-R

--relative[=<path>]

-a, --text

--ignore-space-at-eol

-b, --ignore-space-change

-w, --ignore-all-space

--inter-hunk-context=<lines>

--exit-code

--quiet

--ext-diff

--no-ext-diff

--ignore-submodules

--src-prefix=<prefix>

--dst-prefix=<prefix>

--no-prefix

For more detailed explanation on these common options, see also gitdiffcore(7).

<tree-ish>

--cached

-m

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>

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

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

git-diff-files [<pattern>...]

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:

Possible status letters are:

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:

Example:

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

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

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.

diff --git a/file1 b/file2

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>

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.

COMBINED DIFF FORMAT¶

"git-diff-tree", "git-diff-files" and "git-diff" can take -c or --cc option to produce combined diff. For showing a merge commit with "git log -p", this is the default format; you can force showing full diff with the -m option. 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);

diff --combined file

diff --cc file

index <hash>,<hash>..<hash>
mode <mode>,<mode>..<mode>
new file mode <mode>
deleted file mode <mode>,<mode>

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

@@@ <from-file-range> <from-file-range> <to-file-range> @@@

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").

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:

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 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.

OPERATING MODES¶

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.

CACHED MODE¶

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 using ´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, 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 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 see easily 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".

NON-CACHED MODE¶

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

i.e., 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.

AUTHOR¶

Written by Linus Torvalds <torvalds@osdl.org[1]>

DOCUMENTATION¶

Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org[2]>.

GIT¶

Part of the git(1) suite

NOTES¶

1.

torvalds@osdl.org

2.

git@vger.kernel.org