GIT-DIFF-INDEX(1)

💖 GIT-DIFF-INDEX(1) 💖

okay bestie so this is from the Git Manual — like, the official one, not a fan wiki. welcome to git-diff-index, she's a little niche but she's lowkey iconic 🎀

✨ NAME ✨

git-diff-index — compares a tree to the working tree or the index. that's it, that's the whole vibe check 🦋

🌸 SYNOPSIS 🌸

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

💅 DESCRIPTION 💅

so what she actually does: she compares the content and mode of the blobs chillin' inside a tree object against the matching tracked files in your working tree — OR against the matching paths in the index. pick your fighter bestie ✨

and if you pass <path> arguments, she only compares paths that match those patterns — otherwise she's comparing all tracked files. no cap. 🫶

🦋 OPTIONS 🦋

-p, -u, --patch — produces a patch, fr fr. (the deets live in the section called "GENERATING PATCH TEXT WITH -P" iykyk)
-s, --no-patch — shuts all the diff machinery's output down completely. useful for commands like git show that spit out a patch by default and you're like "not today 😭", or to cancel the effect of earlier --patch, --stat style options sitting earlier on the command line in an alias.
-U<n>, --unified=<n> — makes diffs with <n> lines of context, periodt. default number of context lines is diff.context, or 3 if that config variable isn't set. (fun fact: -U with no <n> is silently accepted as a synonym for -p because of a historical accident 🙈 iconic messy behaviour). implies --patch.
--output=<file> — sends the output to a specific file instead of stdout. slay.
--output-indicator-new=<char>, --output-indicator-old=<char>, --output-indicator-context=<char> — picks the character that marks new, old, or context lines in the generated patch. normally those are +, - and ' ' respectively. 💅
--raw — generates the diff in raw format. this is the default, so she's the main character already 👑
--patch-with-raw — synonym for -p --raw.
--indent-heuristic — turns on the heuristic that shifts diff hunk boundaries so patches are easier to read. also the default, bestie ✨
--no-indent-heuristic — turns the indent heuristic off. that's it.
--minimal — spends extra time making sure the smallest possible diff comes out. she's thorough, okay? 💀
--patience — makes a diff using the "patience diff" algorithm.
--histogram — makes a diff using the "histogram diff" algorithm.
--anchored=<text> — makes 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 tries to prevent it from showing up as a deletion or addition in the output. internally it uses the "patience diff" algorithm. cute.
--diff-algorithm=(patience|minimal|histogram|myers) — picks a diff algorithm. the variants are:
- default, myers — the basic greedy diff algorithm. currently the default one.
- minimal — spends extra time making sure the smallest possible diff is produced.
- patience — uses the "patience diff" algorithm when generating patches.
- histogram — extends the patience algorithm to "support low-occurrence common elements".
- so like, if you set the diff.algorithm variable to a non-default value and you want the default one back, you gotta use --diff-algorithm=default. yes really 🌈
--stat[=<width>[,<name-width>[,<count>]]] — generates a diffstat 📊. by default as much space as necessary goes to the filename part and the rest to the graph part. maximum width defaults to terminal width, or 80 columns if you're not connected to a terminal, and <width> overrides it. the filename part's width can be limited by giving another width <name-width> after a comma, or by setting diff.statNameWidth=<name-width>. the graph part's width can be limited with --stat-graph-width=<graph-width> or by setting diff.statGraphWidth=<graph-width>. using --stat or --stat-graph-width affects all commands that generate a stat graph, whereas setting diff.statNameWidth or diff.statGraphWidth does not affect git format-patch. and if you give 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 — outputs a condensed summary of extended header info — like file creations or deletions ("new" or "gone", optionally +l if it's a symlink) and mode changes (+x or -x for adding or removing the executable bit respectively) — right there in the diffstat. the info goes between the filename part and the graph part. implies --stat. 🍓
--numstat — like --stat but shows the number of added and deleted lines in decimal notation, with the pathname unabbreviated, so it's more machine friendly 🤖. for binary files it outputs two - instead of saying 0 0.
--shortstat — outputs only the last line of the --stat format, containing the total number of modified files plus the number of added and deleted lines. short and sweet.
-X [<param>,...], --dirstat[=<param>,...] — outputs the distribution of the relative amount of changes for each sub-directory. you can customise --dirstat's behaviour by passing it a comma-separated list of parameters. the defaults are controlled by the diff.dirstat configuration variable (see git-config(1)). the parameters available are:
- changes — computes the dirstat numbers by counting the lines removed from the source, or added to the destination. this ignores the amount of pure code movements within a file — like, rearranging lines in a file isn't counted as much as other changes. this is the default behaviour when you give no parameter.
- lines — computes 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 behaviour than changes, 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 — computes 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 behaviour since it doesn't have to look at file contents at all 💅.
- cumulative — counts changes in a child directory for the parent directory too. note that when using cumulative, the sum of the reported percentages may exceed 100% 😳. the default (non-cumulative) behaviour can be specified with the noncumulative parameter.
- <limit> — an integer parameter specifying a cut-off percent (3% by default). directories contributing less than this percentage of the changes just don't show up in the output.
- example: the following counts changed files while ignoring directories with less than 10% of the total amount of changed files, and accumulating child directory counts into the parent directories: --dirstat=files,10,cumulative. ✨
--cumulative — synonym for --dirstat=cumulative.
--dirstat-by-file[=<param>,...] — synonym for --dirstat=files,<param>,....
--summary — outputs a condensed summary of extended header info such as creations, renames and mode changes. yes, like --compact-summary's cousin.
--patch-with-stat — synonym for -p --stat.
-z — when --raw, --numstat, --name-only or --name-status has been given, don't munge pathnames and use NULs as output field terminators.
- without this option, pathnames with "unusual" characters get quoted, as explained for the configuration variable core.quotePath (see git-config(1)).
--name-only — shows only the name of each changed file in the post-image tree. the file names are often encoded in UTF-8. for more info see the discussion about encoding in the git-log(1) manual page 📖.
--name-status — shows only the name(s) and status of each changed file. see the description of the --diff-filter option for what the status letters mean. just like --name-only, the file names are often encoded in UTF-8.
--submodule[=<format>] — specifies how differences in submodules are shown 🧚. when you specify --submodule=short the short format is used — that one 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, which lists the commits in the range like git-submodule(1) summary does. when --submodule=diff is specified, the diff format is used — that one 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>] — shows a colored diff 🌈. --color (i.e. without =<when>) is the same as --color=always. <when> can be one of always, never, or auto.
--no-color — turns colored diff off. same as --color=never.
--color-moved[=<mode>] — moved lines of code get colored differently 👀. <mode> defaults to no if the option isn't given, and to zebra if the option is given with no mode. the mode must be one of:
- no — moved lines aren't highlighted.
- default — a synonym for zebra. this may change to a more sensible mode in the future, so don't get too attached.
- plain — any line added in one location and removed in another location gets colored with color.diff.newMoved. similarly color.diff.oldMoved is used for removed lines that are added somewhere else in the diff. this mode picks up any moved line, but it's not very useful in a review to determine if a block of code was moved without permutation tbh.
- 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 can't be told apart.
- zebra — blocks of moved text are detected like 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 a new block was detected 🦓✨

okay that's the first chunk — more coming, don't go anywhere bestie 💜

dimmed-zebra — okay so this is like zebra, but it does extra dimming of the uninteresting parts of moved code 💅 the bordering lines of two adjacent blocks count as interesting, and the rest is uninteresting. also dimmed_zebra is a deprecated synonym, bestie.
--no-color-moved — turns off move detection entirely. use this to override config settings; it’s literally the same as --color-moved=no 🫶
--color-moved-ws=<mode>,... — this configures how whitespace gets ignored when doing 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 the 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’s the same as --color-moved-ws=no 😌
--word-diff[=<mode>] — by default, words are delimited by whitespace; see --word-diff-regex below. <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 💖

the --word-diff option operates by taking the same line-by-line diff that is produced without the option and computing word-by-word changes within each hunk. this may produce a larger diff than a dedicated word-diff tool would. if Git acquires a different implementation in the future, the output may change. note that this is similar to the --diff-algorithm option, which may also change the output 👀

--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. periodt.
--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. not me forgetting this exists 💀
--rename-empty, --no-rename-empty — whether to use empty blobs as rename source 🎀
--check — warn if changes introduce conflict markers or whitespace errors. what counts as 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:
1. 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).
2. 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, the -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> — okay so this one hunts for diffs that change how many times <string> shows up in a file (like additions/deletions of it). It’s made for the script girlies 💅

It’s iconic when you’re chasing an exact block of code (say, a struct) and wanna know its whole history since it first appeared: feed the interesting block from the preimage back into -S over and over until you hit the very first version of that block. Literally detective mode 🔍

Binary files are searched too, no cap.

-G<regex> — looks for diffs whose patch text has added/removed lines matching <regex>.

To show the difference between -S<regex> --pickaxe-regex and -G<regex>, think of a commit with this diff in the same file:

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

git log -G"frotz\(nitfol" will show this commit, but git log -S"frotz\(nitfol" --pickaxe-regex will not — because the number of occurrences of that string didn’t change. periodt.

Unless --text is supplied, patches of binary files without a textconv filter are ignored.

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

--find-object=<object-id> — looks for diffs that change how many times the specified object occurs. Similar to -S, except the argument is different: it doesn’t search for a specific string, it searches for a specific object id.

The object can be a blob or a submodule commit. It implies the -t option in git-log so trees get found too.

--pickaxe-all — when -S or -G finds a change, show all the changes in that changeset, not just the files containing the change in <string>.
--pickaxe-regex — treat the <string> given to -S as an extended POSIX regular expression to match.
-O<orderfile> — controls the order files appear in the output. This overrides the diff.orderFile config 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 whose pathnames match the first pattern come out first, all files matching the second pattern (but not the first) come next, and so on. All files that match no pattern come out last, as if there’s an implicit match-all pattern at the end. If multiple pathnames have the same rank (same pattern, no earlier patterns), their order relative to each other is the normal order.

<orderfile> is parsed like this:

Blank lines are ignored, so you can use them as separators for readability.
Lines starting with a hash ("#") are ignored, so you can use them for comments. Add a backslash ("\") to the beginning of the pattern if it starts with a hash.
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". slay.

--skip-to=<file>, --rotate-to=<file> — discard the files before the named <file> from the output (that’s skip to), or move them to the end of the output (that’s rotate to). These options were invented primarily for the git difftool command, and may not be very useful otherwise. iykyk.
-R — swap the two inputs; that is, show differences from the index or on-disk file to tree contents.
--relative[=<path>], --no-relative — when you run this from a subdirectory of the project, you can tell it to exclude changes outside that directory and show pathnames relative to it with this option. When you’re 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 the diff.relative config option and a 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 the 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 lines all 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 the whole function as context lines for each change. The function names are determined in the same way git diff works out patch hunk headers (see "Defining a custom hunk-header" in gitattributes(5)). main character energy for your diff.
--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. important bestie 🫶
--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, and 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. ⚠️
--max-depth=<depth> — for each pathspec given on the command line, descend at most <depth> levels of directories. A value of -1 means no limit. Cannot be combined with wildcards in the pathspec. Given a tree containing foo/bar/baz, this list shows the matches generated by each set of options:
- --max-depth=0 -- foo: foo
- --max-depth=1 -- foo: foo/bar
- --max-depth=1 -- foo/bar: foo/bar/baz
- --max-depth=1 -- foo foo/bar: foo/bar/baz
- --max-depth=2 -- foo: foo/bar/baz

If no pathspec is given, the depth is measured as if all top-level entries were specified. Note that this is different than measuring from the root, in that --max-depth=0 would still return foo. This allows you to still limit depth while asking for a subset of the top-level entries.

Note that this option is only supported for diffs between tree objects, not against the index or working tree.

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 🦋

okay bestie, so the raw output from git-diff-index, git-diff-tree, git-diff-files, and git diff --raw is very similar — like, same vibe, different little details. 💅

These commands all compare two sets of things; what gets compared is the part that changes:

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. 🦋

All the commands print one output line per changed file, except git diff-files in the case of an unmerged file, which prints both an "unmerged" and an "in-place edit" line. noted, bestie 👑

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 if "src" is from the index and is unmerged.
a space.
mode for "dst"; 000000 if deletion, or if "dst" is from the index and is unmerged.
a space.
sha1 for "src"; 0{40} if creation, or if "src" is from the index and is unmerged.
a space.
sha1 for "dst"; 0{40} if deletion, if "dst" is from the index and is unmerged, or if "dst" is from the work tree and is out of sync with the index.
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.

Possible status letters are:

A: addition of a file 🍓
C: copy of a file into a new one
D: deletion of a file 💀
M: modification of the contents or mode of a file
R: renaming of a file
T: change in the type of the file (regular file, symbolic link or submodule)
U: file is unmerged (you must complete the merge before it can be committed) 😭
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. iykyk ✨

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. periodt 💅

🌈 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:

there is a colon for each parent 🎀
there are more "src" modes and "src" sha1
status is concatenated status characters for each parent
no optional "score" number
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. obsessed with the detail tbh 🦋

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)). slay, customizable patch text ✨

What the -p option produces is slightly different from the traditional diff format:

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. iconic behavior 🫶

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.

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. math but make it cute 💅

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.

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

bestie do NOT apply these one by one, that is literally not the vibe 😭

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 ✨

okay so literally any diff-generating command can take the -c or --cc option to produce a combined diff when it’s showing a merge 💅. This is the default format when showing merges with git-diff(1) or git-show(1). Also note: you can give a suitable --diff-merges option to any of these commands to force generation of diffs in a specific format. slay.

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);

It is preceded by a “git diff” header, and it looks like this when the -c option is used:

    diff --combined file

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

    diff --cc file

It is followed by one or more extended header lines — this example shows a merge with two parents:

    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. no cap.

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. 💖

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. periodt.

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 +). iconic.

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. bestie, they’re for ur eyeballs.

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:

the number of added lines;
a tab;
the number of deleted lines;
a tab;
pathname (possibly with rename/copy information);
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:

the number of added lines;
a tab;
the number of deleted lines;
a tab;
a NUL (only exists if renamed/copied);
pathname in preimage;
a NUL (only exists if renamed/copied);
pathname in postimage (only exists if renamed/copied);
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. iykyk 🔥

🦋 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. ate.

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. 🧚

okay bye bestie! this whole vibe was brought to you by Git 2.56.0, dated 2026-09-27 💖✨🎀

📦 where this page comes from

arch rolling: git 2.56.0-1 · GPL-2.0-only
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-06: a language model's rewrite of the original, under its terms