git-diff-index(1)

NAME#

git-diff-index - Compare a tree to the working tree or index

SYNOPSIS#

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

DESCRIPTION#

Compare the content and mode of the blobs found in a tree object with the corresponding tracked files in the working tree, or with the corresponding paths in the index. When <path> arguments are present, compare only paths matching those patterns. Otherwise all tracked files are compared.

OPTIONS#

-p, -u, --patch

-s, --no-patch

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

--output=<file>

--output-indicator-new=<char>, --output-indicator-old=<char>, --output-indicator-context=<char>

--raw

--patch-with-raw

--indent-heuristic

--no-indent-heuristic

--minimal

--patience

--histogram

--anchored=<text>

This option may be specified more than once.

If a line exists in both the source and destination, exists only once, and starts with this text, this algorithm attempts to prevent it from appearing as a deletion or addition in the output. It uses the "patience diff" algorithm internally.

--diff-algorithm={patience|minimal|histogram|myers}

default, myers

minimal

patience

histogram

For instance, if you configured the diff.algorithm variable to a non-default value and want to use the default one, then you have to use --diff-algorithm=default option.

--stat[=<width>[,<name-width>[,<count>]]]

These parameters can also be set individually with --stat-width=<width>, --stat-name-width=<name-width> and --stat-count=<count>.

--compact-summary

--numstat

--shortstat

-X[<param1,param2,...>], --dirstat[=<param1,param2,...>]

changes

lines

files

cumulative

<limit>

Example: The following will count changed files, while ignoring directories with less than 10% of the total amount of changed files, and accumulating child directory counts in the parent directories: --dirstat=files,10,cumulative.

--cumulative

--dirstat-by-file[=<param1,param2>...]

--summary

--patch-with-stat

-z

Without this option, pathnames with "unusual" characters are quoted as explained for the configuration variable core.quotePath (see git-config(1)).

--name-only

--name-status

--submodule[=<format>]

--color[=<when>]

--no-color

--color-moved[=<mode>]

no

default

plain

blocks

zebra

dimmed-zebra

--no-color-moved

--color-moved-ws=<modes>

no

ignore-space-at-eol

ignore-space-change

ignore-all-space

allow-indentation-change

--no-color-moved-ws

--word-diff[=<mode>]

color

plain

porcelain

none

Note that despite the name of the first mode, color is used to highlight the changed parts in all modes if enabled.

--word-diff-regex=<regex>

Every non-overlapping match of the <regex> is considered a word. Anything between these matches is considered whitespace and ignored(!) for the purposes of finding differences. You may want to append |[^[:space:]] to your regular expression to make sure that it matches all non-whitespace characters. A match that contains a newline is silently truncated(!) at the newline.

For example, --word-diff-regex=. will treat each character as a word and, correspondingly, show differences character by character.

The regex can also be set via a diff driver or configuration option, see gitattributes(5) or git-config(1). Giving it explicitly overrides any diff driver or configuration setting. Diff drivers override configuration settings.

--color-words[=<regex>]

--no-renames

--[no-]rename-empty

--check

--ws-error-highlight=<kind>

--full-index

--binary

--abbrev[=<n>]

-B[<n>][/<m>], --break-rewrites[=[<n>][/<m>]]

It affects the way a change that amounts to a total rewrite of a file not as a series of deletion and insertion mixed together with a very few lines that happen to match textually as the context, but as a single deletion of everything old followed by a single insertion of everything new, and the number m controls this aspect of the -B option (defaults to 60%). -B/70% specifies that less than 30% of the original should remain in the result for Git to consider it a total rewrite (i.e. otherwise the resulting patch will be a series of deletion and insertion mixed together with context lines).

When used with -M, a totally-rewritten file is also considered as the source of a rename (usually -M only considers a file that disappeared as the source of a rename), and the number n controls this aspect of the -B option (defaults to 50%). -B20% specifies that a change with addition and deletion compared to 20% or more of the file’s size are eligible for being picked up as a possible source of a rename to another file.

-M[<n>], --find-renames[=<n>]

-C[<n>], --find-copies[=<n>]

--find-copies-harder

-D, --irreversible-delete

When used together with -B, omit also the preimage in the deletion part of a delete/create pair.

-l<num>

--diff-filter=[(A|C|D|M|R|T|U|X|B)...[*]]

Also, these upper-case letters can be downcased to exclude. E.g. --diff-filter=ad excludes added and deleted paths.

Note that not all diffs can feature all types. For instance, copied and renamed entries cannot appear if detection for those types is disabled.

-S<string>

It is useful when you’re looking for an exact block of code (like a struct), and want to know the history of that block since it first came into being: use the feature iteratively to feed the interesting block in the preimage back into -S, and keep going until you get the very first version of the block.

Binary files are searched as well.

-G<regex>

To illustrate the difference between -S<regex> --pickaxe-regex and -G<regex>, consider a commit with the following diff in the same file:

+    return frotz(nitfol, two->ptr, 1, 0);
...
-    hit = frotz(nitfol, mf2.ptr, 1, 0);

While git log -G"frotz\(nitfol" will show this commit, git log -S"frotz\(nitfol" --pickaxe-regex will not (because the number of occurrences of that string did not change).

Unless --text is supplied patches of binary files without a textconv filter will be ignored.

See the pickaxe entry in gitdiffcore(7) for more information.

--find-object=<object-id>

The object can be a blob or a submodule commit. It implies the -t option in git-log to also find trees.

--pickaxe-all

--pickaxe-regex

-O<orderfile>

The output order is determined by the order of glob patterns in <orderfile>. All files with pathnames that match the first pattern are output first, all files with pathnames that match the second pattern (but not the first) are output next, and so on. All files with pathnames that do not match any pattern are output last, as if there was an implicit match-all pattern at the end of the file. If multiple pathnames have the same rank (they match the same pattern but no earlier patterns), their output order relative to each other is the normal order.

<orderfile> is parsed as follows:

Patterns have the same syntax and semantics as patterns used for fnmatch(3) without the FNM_PATHNAME flag, except a pathname also matches a pattern if removing any number of the final pathname components matches the pattern. For example, the pattern "foo*bar" matches "fooasdfbar" and "foo/bar/baz/asdf" but not "foobarx".

--skip-to=<file>, --rotate-to=<file>

-R

--relative[=<path>], --no-relative

-a, --text

--ignore-cr-at-eol

--ignore-space-at-eol

-b, --ignore-space-change

-w, --ignore-all-space

--ignore-blank-lines

-I<regex>, --ignore-matching-lines=<regex>

--inter-hunk-context=<lines>

-W, --function-context

--exit-code

--quiet

--ext-diff

--no-ext-diff

--textconv, --no-textconv

--ignore-submodules[=<when>]

--src-prefix=<prefix>

--dst-prefix=<prefix>

--no-prefix

--default-prefix

--line-prefix=<prefix>

--ita-invisible-in-index

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

<tree-ish>

--cached

--merge-base

-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). 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:

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:

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.

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.

diff --git a/a b/b
rename from a
rename to b
diff --git a/b b/a
rename from b
rename to a

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 @@@
\n
        return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
\n
  }
- static void describe(char *arg)
\n
 -static void describe(struct commit *cmit, int last_one)
++static void describe(char *arg, int last_one)
\n
  {
\n
 +      unsigned char sha1[20];
\n
 +      struct commit *cmit;
\n
        struct commit_list *list;
\n
        static int initialized = 0;
\n
        struct commit_name *n;
\n
 +      if (get_sha1(arg, sha1) < 0)
\n
 +              usage(describe_usage);
\n
 +      cmit = lookup_commit_reference(sha1);
\n
 +      if (!cmit)
\n
 +              usage(describe_usage);
\n
 +
\n
        if (!initialized) {
\n
                initialized = 1;
\n
                for_each_ref(get_name);

diff --combined file

or like this (when the --cc option is used):

diff --cc file

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.

--- 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.

@@@ <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:

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 000000 4161aecc6700a2eb579e842af0b7f22b98443f74 0000000000000000000000000000000000000000 D    commit.c
:000000 100644 0000000000000000000000000000000000000000 4161aecc6700a2eb579e842af0b7f22b98443f74 A    git-commit.c

You can see easily that the above is a rename.

In fact, git diff-index --cachedshould 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 --abbrev HEAD
:100644 100644 7476bb5ba 000000000 M  kernel/sched.c

i.e., it shows that the tree has changed, and that kernel/sched.c 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.

GIT#

Part of the git(1) suite