GIT-DIFF-INDEX(1) Git Manual GIT-DIFF-INDEX(1)

NAME

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

SYNOPSIS

git diff-index [-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
Generate patch (see the section called "GENERATING PATCH TEXT
WITH -P").

-s, --no-patch
Suppress all output from the diff machinery. Useful for commands
like git show that show the patch by default to squelch their
output, or to cancel the effect of options like --patch, --stat
earlier on the command line in an alias.

-U<n>, --unified=<n>
Generate diffs with <n> lines of context instead of the usual
three. Implies --patch.

--output=<file>
Output to a specific file instead of stdout.

--output-indicator-new=<char>, --output-indicator-old=<char>,
--output-indicator-context=<char>
Specify the character used to indicate new, old or context lines
in the generated patch. Normally they are +, - and ' '
respectively.

--raw
Generate the diff in raw format. This is the default.

--patch-with-raw
Synonym for -p --raw.

--indent-heuristic
Enable the heuristic that shifts diff hunk boundaries to make
patches easier to read. This is the default.

--no-indent-heuristic
Disable the indent heuristic.

--minimal
Spend extra time to make sure the smallest possible diff is
produced.

--patience
Generate a diff using the "patience diff" algorithm.

--histogram
Generate a diff using the "histogram diff" algorithm.

--anchored=<text>
Generate a diff using the "anchored diff" algorithm.

This option may be specified more than once.

If a line exists in both the source and destination, exists only
once, and starts with <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)
Choose a diff algorithm. The variants are as follows:

default, myers
The basic greedy diff algorithm. Currently, this is the
default.

minimal
Spend extra time to make sure the smallest possible diff is
produced.

patience
Use "patience diff" algorithm when generating patches.

histogram
This algorithm extends the patience algorithm to "support
low-occurrence common elements".

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>]]]
Generate a diffstat. By default, as much space as necessary will
be used for the filename part, and the rest for the graph part.
Maximum width defaults to terminal width, or 80 columns if not
connected to a terminal, and can be overridden by <width>. The
width of the filename part can be limited by giving another width
<name-width> after a comma or by setting
diff.statNameWidth=<name-width>. The width of the graph part can
be limited by using --stat-graph-width=<graph-width> or by
setting diff.statGraphWidth=<graph-width>. Using --stat or
--stat-graph-width affects all commands generating a stat graph,
while setting diff.statNameWidth or diff.statGraphWidth does not
affect git format-patch. By giving a third parameter <count>, you
can limit the output to the first <count> lines, followed by ...
if there are more.

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

--compact-summary
Output a condensed summary of extended header information such as
file creations or deletions ("new" or "gone", optionally +l if
it's a symlink) and mode changes (+x or -x for adding or removing
executable bit respectively) in diffstat. The information is put
between the filename part and the graph part. Implies --stat.

--numstat
Similar to --stat, but shows number of added and deleted lines in
decimal notation and pathname without abbreviation, to make it
more machine friendly. For binary files, outputs two - instead of
saying 0 0.

--shortstat
Output only the last line of the --stat format containing total
number of modified files, as well as number of added and deleted
lines.

-X [<param>,...], --dirstat[=<param>,...]
Output the distribution of relative amount of changes for each
sub-directory. The behavior of --dirstat can be customized by
passing it a comma separated list of parameters. The defaults are
controlled by the diff.dirstat configuration variable (see git-
config(1)). The following parameters are available:

changes
Compute the dirstat numbers by counting the lines that have
been removed from the source, or added to the destination.
This ignores the amount of pure code movements within a file.
In other words, rearranging lines in a file is not counted as
much as other changes. This is the default behavior when no
parameter is given.

lines
Compute the dirstat numbers by doing the regular line-based
diff analysis, and summing the removed/added line counts.
(For binary files, count 64-byte chunks instead, since binary
files have no natural concept of lines). This is a more
expensive --dirstat behavior than the changes behavior, but
it does count rearranged lines within a file as much as other
changes. The resulting output is consistent with what you get
from the other --*stat options.

files
Compute the dirstat numbers by counting the number of files
changed. Each changed file counts equally in the dirstat
analysis. This is the computationally cheapest --dirstat
behavior, since it does not have to look at the file contents
at all.

cumulative
Count changes in a child directory for the parent directory
as well. Note that when using cumulative, the sum of the
percentages reported may exceed 100%. The default
(non-cumulative) behavior can be specified with the
noncumulative parameter.

<limit>
An integer parameter specifies a cut-off percent (3% by
default). Directories contributing less than this percentage
of the changes are not shown in the output.

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
Synonym for --dirstat=cumulative.

--dirstat-by-file[=<param>,...]
Synonym for --dirstat=files,<param>,....

--summary
Output a condensed summary of extended header information such as
creations, renames and mode changes.

--patch-with-stat
Synonym for -p --stat.

-z
When --raw, --numstat, --name-only or --name-status has been
given, do not munge pathnames and use NULs as output field
terminators.

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

--name-only
Show only the name of each changed file in the post-image tree.
The file names are often encoded in UTF-8. For more information
see the discussion about encoding in the git-log(1) manual page.

--name-status
Show only the name(s) and status of each changed file. See the
description of the --diff-filter option on what the status
letters mean. Just like --name-only the file names are often
encoded in UTF-8.

--submodule[=<format>]
Specify how differences in submodules are shown. When specifying
--submodule=short the short format is used. This format just
shows the names of the commits at the beginning and end of the
range. When --submodule or --submodule=log is specified, the log
format is used. This format lists the commits in the range like
git-submodule(1) summary does. When --submodule=diff is
specified, the diff format is used. This format shows an inline
diff of the changes in the submodule contents between the commit
range. Defaults to diff.submodule or the short format if the
config option is unset.

--color[=<when>]
Show colored diff. --color (i.e. without =<when>) is the same as
--color=always. <when> can be one of always, never, or auto.

--no-color
Turn off colored diff. It is the same as --color=never.

--color-moved[=<mode>]
Moved lines of code are colored differently. The <mode> defaults
to no if the option is not given and to zebra if the option with
no mode is given. The mode must be one of:

no
Moved lines are not highlighted.

default
Is a synonym for zebra. This may change to a more sensible
mode in the future.

plain
Any line that is added in one location and was removed in
another location will be colored with color.diff.newMoved.
Similarly color.diff.oldMoved will be used for removed lines
that are added somewhere else in the diff. This mode picks up
any moved line, but it is not very useful in a review to
determine if a block of code was moved without permutation.

blocks
Blocks of moved text of at least 20 alphanumeric characters
are detected greedily. The detected blocks are painted using
either the color.diff.(old|new)Moved color. Adjacent blocks
cannot be told apart.

zebra
Blocks of moved text are detected as in blocks mode. The
blocks are painted using either the color.diff.(old|new)Moved
color or color.diff.(old|new)MovedAlternative. The change
between the two colors indicates that a new block was
detected.

dimmed-zebra
Similar to zebra, but additional dimming of uninteresting
parts of moved code is performed. The bordering lines of two
adjacent blocks are considered interesting, the rest is
uninteresting. dimmed_zebra is a deprecated synonym.

--no-color-moved
Turn off move detection. This can be used to override
configuration settings. It is the same as --color-moved=no.

--color-moved-ws=<mode>,...
This configures how whitespace is ignored when performing the
move detection for --color-moved. These modes can be given as a
comma separated list:

no
Do not ignore whitespace when performing move detection.

ignore-space-at-eol
Ignore changes in whitespace at EOL.

ignore-space-change
Ignore changes in amount of whitespace. This ignores
whitespace at line end, and considers all other sequences of
one or more whitespace characters to be equivalent.

ignore-all-space
Ignore whitespace when comparing lines. This ignores
differences even if one line has whitespace where the other
line has none.

allow-indentation-change
Initially ignore any whitespace in the move detection, then
group the moved code blocks only into a block if the change
in whitespace is the same per line. This is incompatible with
the other modes.

--no-color-moved-ws
Do not ignore whitespace when performing move detection. This can
be used to override configuration settings. It is the same as
--color-moved-ws=no.

--word-diff[=<mode>]
By default, words are delimited by whitespace; see
--word-diff-regex below. The <mode> defaults to plain, and must
be one of:

color
Highlight changed words using only colors. Implies --color.

plain
Show words as [-removed-] and {added}. Makes no attempts to
escape the delimiters if they appear in the input, so the
output may be ambiguous.

porcelain
Use a special line-based format intended for script
consumption. Added/removed/unchanged runs are printed in the
usual unified diff format, starting with a +/-/` ` character
at the beginning of the line and extending to the end of the
line. Newlines in the input are represented by a tilde ~ on a
line of its own.

none
Disable word diff again.

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>
Use <regex> to decide what a word is, instead of considering runs
of non-whitespace to be a word. Also implies --word-diff unless
it was already enabled.

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>]
Equivalent to --word-diff=color plus (if a regex was specified)
--word-diff-regex=<regex>.

--no-renames
Turn off rename detection, even when the configuration file gives
the default to do so.

--[no-]rename-empty
Whether to use empty blobs as rename source.

--check
Warn if changes introduce conflict markers or whitespace errors.
What are considered whitespace errors is controlled by
core.whitespace configuration. By default, trailing whitespaces
(including lines that consist solely of whitespaces) and a space
character that is immediately followed by a tab character inside
the initial indent of the line are considered whitespace errors.
Exits with non-zero status if problems are found. Not compatible
with --exit-code.

--ws-error-highlight=<kind>
Highlight whitespace errors in the context, old or new lines of
the diff. Multiple values are separated by comma, none resets
previous values, default reset the list to new and all is a
shorthand for old,new,context. When this option is not given, and
the configuration variable diff.wsErrorHighlight is not set, only
whitespace errors in new lines are highlighted. The whitespace
errors are colored with color.diff.whitespace.

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

--binary
In addition to --full-index, output a binary diff that can be
applied with git-apply. Implies --patch.

--abbrev[=<n>]
Instead of showing the full 40-byte hexadecimal object name in
diff-raw format output and diff-tree header lines, show the
shortest prefix that is at least <n> hexdigits long that uniquely
refers the object. In diff-patch output format, --full-index
takes higher precedence, i.e. if --full-index is specified, full
blob names will be shown regardless of --abbrev. Non default
number of digits can be specified with --abbrev=<n>.

-B[<n>][/<m>], --break-rewrites[=[<n>][/<m>]]
Break complete rewrite changes into pairs of delete and create.
This serves two purposes:

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>]
Detect renames. If <n> is specified, it is a threshold on the
similarity index (i.e. amount of addition/deletions compared to
the file's size). For example, -M90% means Git should consider a
delete/add pair to be a rename if more than 90% of the file
hasn't changed. Without a % sign, the number is to be read as a
fraction, with a decimal point before it. I.e., -M5 becomes 0.5,
and is thus the same as -M50%. Similarly, -M05 is the same as
-M5%. To limit detection to exact renames, use -M100%. The
default similarity index is 50%.

-C[<n>], --find-copies[=<n>]
Detect copies as well as renames. See also --find-copies-harder.
If <n> is specified, it has the same meaning as for -M<n>.

--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. Giving more
than one -C option has the same effect.

-D, --irreversible-delete
Omit the preimage for deletes, i.e. print only the header but not
the diff between the preimage and /dev/null. The resulting patch
is not meant to be applied with patch or git apply; this is
solely for people who want to just concentrate on reviewing the
text after the change. In addition, the output obviously lacks
enough information to apply such a patch in reverse, even
manually, hence the name of the option.

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

-l<num>
The -M and -C options involve some preliminary steps that can
detect subsets of renames/copies cheaply, followed by an
exhaustive fallback portion that compares all remaining unpaired
destinations to all relevant sources. (For renames, only
remaining unpaired sources are relevant; for copies, all original
sources are relevant.) For N sources and destinations, this
exhaustive check is O(N^2). This option prevents the exhaustive
portion of rename/copy detection from running if the number of
source/destination files involved exceeds the specified number.
Defaults to diff.renameLimit. Note that a value of 0 is treated
as unlimited.

--diff-filter=[(A|C|D|M|R|T|U|X|B)...[*]]
Select only files that are Added (A), Copied (C), Deleted (D),
Modified (M), Renamed (R), have their type (i.e. regular file,
symlink, submodule, ...) changed (T), are Unmerged (U), are
Unknown (X), or have had their pairing Broken (B). Any
combination of the filter characters (including none) can be
used. When * (All-or-none) is added to the combination, all paths
are selected if there is any file that matches other criteria in
the comparison; if there is no file that matches other criteria,
nothing is selected.

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>
Look for differences that change the number of occurrences of the
specified <string> (i.e. addition/deletion) in a file. Intended
for the scripter's use.

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>
Look for differences whose patch text contains added/removed
lines that match <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>
Look for differences that change the number of occurrences of the
specified object. Similar to -S, just the argument is different
in that it doesn't search for a specific string but for a
specific 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
When -S or -G finds a change, show all the changes in that
changeset, not just the files that contain the change in
<string>.

--pickaxe-regex
Treat the <string> given to -S as an extended POSIX regular
expression to match.

-O<orderfile>
Control the order in which files appear in the output. This
overrides the diff.orderFile configuration variable (see git-
config(1)). To cancel diff.orderFile, use -O/dev/null.

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:

+o Blank lines are ignored, so they can be used as separators
for readability.

+o Lines starting with a hash ("#") are ignored, so they can be
used for comments. Add a backslash ("\") to the beginning of
the pattern if it starts with a hash.

+o Each other line contains a single pattern.

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>
Discard the files before the named <file> from the output (i.e.
skip to), or move them to the end of the output (i.e. rotate
to). These options were invented primarily for the use of the git
difftool command, and may not be very useful otherwise.

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

--relative[=<path>], --no-relative
When run from a subdirectory of the project, it can be told to
exclude changes outside the directory and show pathnames relative
to it with this option. When you are not in a subdirectory (e.g.
in a bare repository), you can name which subdirectory to make
the output relative to by giving a <path> as an argument.
--no-relative can be used to countermand both diff.relative
config option and previous --relative.

-a, --text
Treat all files as text.

--ignore-cr-at-eol
Ignore carriage-return at the end of line when doing a
comparison.

--ignore-space-at-eol
Ignore changes in whitespace at EOL.

-b, --ignore-space-change
Ignore changes in amount of whitespace. This ignores whitespace
at line end, and considers all other sequences of one or more
whitespace characters to be equivalent.

-w, --ignore-all-space
Ignore whitespace when comparing lines. This ignores differences
even if one line has whitespace where the other line has none.

--ignore-blank-lines
Ignore changes whose lines are all blank.

-I<regex>, --ignore-matching-lines=<regex>
Ignore changes whose all lines match <regex>. This option may be
specified more than once.

--inter-hunk-context=<number>
Show the context between diff hunks, up to the specified <number>
of lines, thereby fusing hunks that are close to each other.
Defaults to diff.interHunkContext or 0 if the config option is
unset.

-W, --function-context
Show whole function as context lines for each change. The
function names are determined in the same way as git diff works
out patch hunk headers (see "Defining a custom hunk-header" in
gitattributes(5)).

--exit-code
Make the program exit with codes similar to diff(1). That is, it
exits with 1 if there were differences and 0 means no
differences.

--quiet
Disable all output of the program. Implies --exit-code. Disables
execution of external diff helpers whose exit code is not
trusted, i.e. their respective configuration option
diff.trustExitCode or diff.<driver>.trustExitCode or environment
variable GIT_EXTERNAL_DIFF_TRUST_EXIT_CODE is false.

--ext-diff
Allow an external diff helper to be executed. If you set an
external diff driver with gitattributes(5), you need to use this
option with git-log(1) and friends.

--no-ext-diff
Disallow external diff drivers.

--textconv, --no-textconv
Allow (or disallow) external text conversion filters to be run
when comparing binary files. See gitattributes(5) for details.
Because textconv filters are typically a one-way conversion, the
resulting diff is suitable for human consumption, but cannot be
applied. For this reason, textconv filters are enabled by default
only for git-diff(1) and git-log(1), but not for git-format-
patch(1) or diff plumbing commands.

--ignore-submodules[=(none|untracked|dirty|all)]
Ignore changes to submodules in the diff generation. all is the
default. Using none will consider the submodule modified when it
either contains untracked or modified files or its HEAD differs
from the commit recorded in the superproject and can be used to
override any settings of the ignore option in git-config(1) or
gitmodules(5). When untracked is used submodules are not
considered dirty when they only contain untracked content (but
they are still scanned for modified content). Using dirty ignores
all changes to the work tree of submodules, only changes to the
commits stored in the superproject are shown (this was the
behavior until 1.7.0). Using all hides all changes to submodules.

--src-prefix=<prefix>
Show the given source <prefix> instead of "a/".

--dst-prefix=<prefix>
Show the given destination <prefix> instead of "b/".

--no-prefix
Do not show any source or destination prefix.

--default-prefix
Use the default source and destination prefixes ("a/" and "b/").
This overrides configuration variables such as diff.noprefix,
diff.srcPrefix, diff.dstPrefix, and diff.mnemonicPrefix (see git-
config(1)).

--line-prefix=<prefix>
Prepend an additional <prefix> to every line of output.

--ita-invisible-in-index
By default entries added by git add -N appear as an existing
empty file in git diff and a new file in git diff --cached. This
option makes the entry appear as a new file in git diff and
non-existent in git diff --cached. This option could be reverted
with --ita-visible-in-index. Both options are experimental and
could be removed in future.

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

<tree-ish>
The id of a tree object to diff against.

--cached
Do not consider the on-disk file at all.

--merge-base
Instead of comparing <tree-ish> directly, use the merge base
between <tree-ish> and HEAD instead. <tree-ish> must be a commit.

-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.

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>
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.

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:

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 deletion, unmerged or "work tree out of
sync with the index".

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.

Possible status letters are:

+o A: addition of a file

+o C: copy of a file into a new one

+o D: deletion of a file

+o M: modification of the contents or mode of a file

+o R: renaming of a file

+o T: change in the type of the file (regular file, symbolic link or
submodule)

+o U: file is unmerged (you must complete the merge before it can be
committed)

+o 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). 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:

1. there is a colon for each parent

2. there are more "src" modes and "src" sha1

3. status is concatenated status characters for each parent

4. no optional "score" number

5. tab-separated pathname(s) of the file

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:

1. It is preceded by 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 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.

2. It is followed by one or more extended header lines:

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 <mode> 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.

3. Pathnames with "unusual" characters are quoted as explained for
the configuration variable core.quotePath (see git-config(1)).

4. All the file1 files in the output refer to files before the
commit, and all the file2 files refer to files after the commit.
It is incorrect to apply each change to each file sequentially.
For example, this patch will swap a and b:

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

5. Hunk headers mention the name of the function to which the hunk
applies. See "Defining a custom hunk-header" in gitattributes(5)
for details of how to tailor this to specific languages.

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 @@@
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);

1. It is preceded by a "git diff" header, that looks like this (when
the -c option is used):

diff --combined file

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

diff --cc file

2. It is followed by one or more extended header lines (this example
shows a merge with two parents):

index <hash>,<hash>`..__<hash>__
{empty}`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.

3. It is followed by a two-line from-file/to-file header:

--- 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.

4. Chunk header format is modified to prevent people from
accidentally feeding it to patch -p1. Combined diff format was
created for review of merge commit changes, and was not meant to
be applied. The change is similar to the change in the extended
index header:

@@@ <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:

1. the number of added lines;

2. a tab;

3. the number of deleted lines;

4. a tab;

5. pathname (possibly with rename/copy information);

6. 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:

1. the number of added lines;

2. a tab;

3. the number of deleted lines;

4. a tab;

5. a NUL (only exists if renamed/copied);

6. pathname in preimage;

7. a NUL (only exists if renamed/copied);

8. pathname in postimage (only exists if renamed/copied);

9. 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.

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 --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 --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.

Note

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.

Note

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

Git 2.48.1 2025-01-13 GIT-DIFF-INDEX(1)