t5526: avoid depending on a specific default branch name

[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[]

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

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

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[]

ifdef::git-log[]
-t::
        Show the tree objects in the diff output.
endif::git-log[]

--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 this text, this algorithm attempts to prevent it from
appearing as a deletion or addition in the output. It uses the "patience
diff" algorithm internally.

--diff-algorithm={patience|minimal|histogram|myers}::
        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. 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>`.

--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[<param1,param2,...>]::
--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`.

--cumulative::
        Synonym for --dirstat=cumulative

--dirstat-by-file[=<param1,param2>...]::
        Synonym for --dirstat=files,param1,param2...

--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, pathnames with "unusual" characters are quoted as
explained for the configuration variable `core.quotePath` (see
linkgit:git-config[1]).

--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 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
        linkgit: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`.
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`.

--color-moved[=<mode>]::
        Moved lines of code are colored differently.
ifdef::git-diff[]
        It can be changed by the `diff.colorMoved` configuration setting.
endif::git-diff[]
        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=<modes>::
        This configures how whitespace is ignored when performing the
        move detection for `--color-moved`.
ifdef::git-diff[]
        It can be set by the `diff.colorMovedWS` configuration setting.
endif::git-diff[]
        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>]::
        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.
+
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
linkgit:gitattributes[5] 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.

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

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

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`.
ifndef::git-format-patch[]
        Implies `--patch`.
endif::git-format-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>]::
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 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 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.
+
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, diffs
from the index to the working tree can never have Added entries
(because the set of paths included in the diff is limited by what is in
the index).  Similarly, 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 linkgit: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.

endif::git-format-patch[]

-O<orderfile>::
        Control the order in which files appear in the output.
        This overrides the `diff.orderFile` configuration variable
        (see linkgit: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:
+
--
 - Blank lines are ignored, so they can be used as separators for
   readability.

 - 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.

 - 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`".

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

--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=<lines>::
        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 linkgit:gitattributes[5]).

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.

--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
linkgit:gitdiffcore[7].