diff: undocument the compaction heuristic knobs for experimentation

[thirdparty/git.git] / Documentation / diff-options.txt

// Please don't remove this comment as asciidoc behaves badly when
// the first non-empty line is ifdef/ifndef. The symptom is that
// without this comment the <git-diff-core> attribute conditionally
// defined below ends up being defined unconditionally.
// Last checked with asciidoc 7.0.2.

ifndef::git-format-patch[]
ifndef::git-diff[]
ifndef::git-log[]
:git-diff-core: 1
endif::git-log[]
endif::git-diff[]
endif::git-format-patch[]

ifdef::git-format-patch[]
-p::
--no-stat::
	Generate plain patches without any diffstats.
endif::git-format-patch[]

ifndef::git-format-patch[]
-p::
-u::
--patch::
	Generate patch (see section on generating patches).
ifdef::git-diff[]
	This is the default.
endif::git-diff[]
endif::git-format-patch[]

-s::
--no-patch::
	Suppress diff output. Useful for commands like `git show` that
	show the patch by default, or to cancel the effect of `--patch`.

-U<n>::
--unified=<n>::
	Generate diffs with <n> lines of context instead of
	the usual three.
ifndef::git-format-patch[]
	Implies `-p`.
endif::git-format-patch[]

ifndef::git-format-patch[]
--raw::
ifndef::git-log[]
	Generate the diff in raw format.
ifdef::git-diff-core[]
	This is the default.
endif::git-diff-core[]
endif::git-log[]
ifdef::git-log[]
	For each commit, show a summary of changes using the raw diff
	format. See the "RAW OUTPUT FORMAT" section of
	linkgit:git-diff[1]. This is different from showing the log
	itself in raw format, which you can achieve with
	`--format=raw`.
endif::git-log[]
endif::git-format-patch[]

ifndef::git-format-patch[]
--patch-with-raw::
	Synonym for `-p --raw`.
endif::git-format-patch[]

--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.

--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 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. The width
	of the graph part can be limited by using
	`--stat-graph-width=<width>` (affects all commands generating
	a stat graph) or by setting `diff.statGraphWidth=<width>`
	(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>`.

--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.

--dirstat[=<param1,param2,...>]::
	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 linkgit: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`.

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

ifndef::git-format-patch[]
--patch-with-stat::
	Synonym for `-p --stat`.
endif::git-format-patch[]

ifndef::git-format-patch[]

-z::
ifdef::git-log[]
	Separate the commits with NULs instead of with new newlines.
+
Also, when `--raw` or `--numstat` has been given, do not munge
pathnames and use NULs as output field terminators.
endif::git-log[]
ifndef::git-log[]
	When `--raw`, `--numstat`, `--name-only` or `--name-status` has been
	given, do not munge pathnames and use NULs as output field terminators.
endif::git-log[]
+
Without this option, each pathname output will have TAB, LF, double quotes,
and backslash characters replaced with `\t`, `\n`, `\"`, and `\\`,
respectively, and the pathname will be enclosed in double quotes if
any of those replacements occurred.

--name-only::
	Show only names of changed files.

--name-status::
	Show only names and status of changed files. See the description
	of the `--diff-filter` option on what the status letters mean.

--submodule[=<format>]::
	Specify how differences in submodules are shown.  When `--submodule`
	or `--submodule=log` is given, the 'log' format is used.  This format lists
	the commits in the range like linkgit:git-submodule[1] `summary` does.
	Omitting the `--submodule` option or specifying `--submodule=short`,
	uses the 'short' format. This format just shows the names of the commits
	at the beginning and end of the range.  Can be tweaked via the
	`diff.submodule` configuration variable.

--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`.
ifdef::git-diff[]
	It can be changed by the `color.ui` and `color.diff`
	configuration settings.
endif::git-diff[]

--no-color::
	Turn off colored diff.
ifdef::git-diff[]
	This can be used to override configuration settings.
endif::git-diff[]
	It is the same as `--color=never`.

--word-diff[=<mode>]::
	Show a word diff, using the <mode> to delimit changed words.
	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.
+
The regex can also be set via a diff driver or configuration option, see
linkgit:gitattributes[1] or linkgit: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>`.
endif::git-format-patch[]

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

ifndef::git-format-patch[]
--check::
	Warn if changes introduce whitespace errors.  What are
	considered whitespace errors is controlled by `core.whitespace`
	configuration.  By default, trailing whitespaces (including
	lines that solely consist 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.
endif::git-format-patch[]

--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`.

--abbrev[=<n>]::
	Instead of showing the full 40-byte hexadecimal object
	name in diff-raw format output and diff-tree header
	lines, show only a partial prefix.  This is
	independent of the `--full-index` option above, which controls
	the diff-patch output format.  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>]::
ifndef::git-log[]
	Detect renames.
endif::git-log[]
ifdef::git-log[]
	If generating diffs, detect and report renames for each commit.
	For following files across renames while traversing history, see
	`--follow`.
endif::git-log[]
	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 lack
	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 require O(n^2) processing time where n
	is the number of potential rename/copy targets.  This
	option prevents rename/copy detection from running if
	the number of rename/copy targets exceeds the specified
	number.

ifndef::git-format-patch[]
--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.

-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.

-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 !regexec(regexp, two->ptr, 1, &regmatch, 0);
...
-    hit = !regexec(regexp, mf2.ptr, 1, &regmatch, 0);
----
+
While `git log -G"regexec\(regexp"` will show this commit, `git log
-S"regexec\(regexp" --pickaxe-regex` will not (because the number of
occurrences of that string did not change).
+
See the 'pickaxe' entry in linkgit:gitdiffcore[7] for more
information.

--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.
endif::git-format-patch[]

-O<orderfile>::
	Output the patch in the order specified in the
	<orderfile>, which has one shell glob pattern per line.
	This overrides the `diff.orderFile` configuration variable
	(see linkgit:git-config[1]).  To cancel `diff.orderFile`,
	use `-O/dev/null`.

ifndef::git-format-patch[]
-R::
	Swap two inputs; that is, show differences from index or
	on-disk file to tree contents.

--relative[=<path>]::
	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.
endif::git-format-patch[]

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

--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.

--inter-hunk-context=<lines>::
	Show the context between diff hunks, up to the specified number
	of lines, thereby fusing hunks that are close to each other.

-W::
--function-context::
	Show whole surrounding functions of changes.

ifndef::git-format-patch[]
ifndef::git-log[]
--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`.
endif::git-log[]
endif::git-format-patch[]

--ext-diff::
	Allow an external diff helper to be executed. If you set an
	external diff driver with linkgit:gitattributes[5], you need
	to use this option with linkgit: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 linkgit: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 linkgit:git-diff[1] and
	linkgit:git-log[1], but not for linkgit:git-format-patch[1] or
	diff plumbing commands.

--ignore-submodules[=<when>]::
	Ignore changes to submodules in the diff generation. <when> can be
	either "none", "untracked", "dirty" or "all", which 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 linkgit:git-config[1] or linkgit: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.

For more detailed explanation on these common options, see also
linkgit:gitdiffcore[7].