The author of fe6e0ee was Junio C Hamano, 23 hours ago
The title was >>t4119: test autocomputing -p<n> for traditional diff input.<<

--------
+
The placeholders are:

- '%H': commit hash
- '%h': abbreviated commit hash
- '%T': tree hash
- '%t': abbreviated tree hash
- '%P': parent hashes
- '%p': abbreviated parent hashes
- '%an': author name
- '%aN': author name (respecting .mailmap, see git-shortlog[1]
  or git-blame[1])
- '%ae': author email
- '%aE': author email (respecting .mailmap, see
  git-shortlog[1] or git-blame[1])
- '%ad': author date (format respects --date= option)
- '%aD': author date, RFC2822 style
- '%ar': author date, relative
- '%at': author date, UNIX timestamp
- '%ai': author date, ISO 8601 format
- '%cn': committer name
- '%cN': committer name (respecting .mailmap, see
  git-shortlog[1] or git-blame[1])
- '%ce': committer email
- '%cE': committer email (respecting .mailmap, see
  git-shortlog[1] or git-blame[1])
- '%cd': committer date
- '%cD': committer date, RFC2822 style
- '%cr': committer date, relative
- '%ct': committer date, UNIX timestamp
- '%ci': committer date, ISO 8601 format
- '%d': ref names, like the --decorate option of git-log[1]
- '%e': encoding
- '%s': subject
- '%f': sanitized subject line, suitable for a filename
- '%b': body
- '%B': raw body (unwrapped subject and body)
- '%N': commit notes
- '%GG': raw verification message from GPG for a signed commit
- '%G?': show "G" for a Good signature, "B" for a Bad signature, "U" for a good,
  untrusted signature and "N" for no signature
- '%GS': show the name of the signer for a signed commit
- '%GK': show the key used to sign a signed commit
- '%gD': reflog selector, e.g., `refs/stash@{1}`
- '%gd': shortened reflog selector, e.g., `stash@{1}`
- '%gn': reflog identity name
- '%gN': reflog identity name (respecting .mailmap, see
  git-shortlog[1] or git-blame[1])
- '%ge': reflog identity email
- '%gE': reflog identity email (respecting .mailmap, see
  git-shortlog[1] or git-blame[1])
- '%gs': reflog subject
- '%Cred': switch color to red
- '%Cgreen': switch color to green
- '%Cblue': switch color to blue
- '%Creset': reset color
- '%C(...)': color specification, as described in color.branch.* config option;
  adding `auto,` at the beginning will emit color only when colors are
  enabled for log output (by `color.diff`, `color.ui`, or `--color`, and
  respecting the `auto` settings of the former if we are going to a
  terminal). `auto` alone (i.e. `%C(auto)`) will turn on auto coloring
  on the next placeholders until the color is switched again.
- '%m': left, right or boundary mark
- '%n': newline
- '%%': a raw '%'
- '%x00': print a byte from a hex code
- '%w([<w>[,<i1>[,<i2>]]])': switch line wrapping, like the -w option of
  git-shortlog[1].
- '%<(<N>[,trunc|ltrunc|mtrunc])': make the next placeholder take at
  least N columns, padding spaces on the right if necessary.
  Optionally truncate at the beginning (ltrunc), the middle (mtrunc)
  or the end (trunc) if the output is longer than N columns.
  Note that truncating only works correctly with N >= 2.
- '%<|(<N>)': make the next placeholder take at least until Nth
  columns, padding spaces on the right if necessary
- '%>(<N>)', '%>|(<N>)': similar to '%<(<N>)', '%<|(<N>)'
  respectively, but padding spaces on the left
- '%>>(<N>)', '%>>|(<N>)': similar to '%>(<N>)', '%>|(<N>)'
  respectively, except that if the next placeholder takes more spaces
  than given and there are spaces on its left, use those spaces
- '%><(<N>)', '%><|(<N>)': similar to '% <(<N>)', '%<|(<N>)'
  respectively, but padding both sides (i.e. the text is centered)

NOTE: Some placeholders may depend on other options given to the
revision traversal engine. For example, the `%g*` reflog options will
insert an empty string unless we are traversing reflog entries (e.g., by
`git log -g`). The `%d` placeholder will use the "short" decoration
format if `--decorate` was not already provided on the command line.

If you add a `+` (plus sign) after '%' of a placeholder, a line-feed
is inserted immediately before the expansion if and only if the
placeholder expands to a non-empty string.

If you add a `-` (minus sign) after '%' of a placeholder, line-feeds that
immediately precede the expansion are deleted if and only if the
placeholder expands to an empty string.

If you add a ` ` (space) after '%' of a placeholder, a space
is inserted immediately before the expansion if and only if the
placeholder expands to a non-empty string.

* 'tformat:'
+
The 'tformat:' format works exactly like 'format:', except that it
provides "terminator" semantics instead of "separator" semantics. In
other words, each commit has the message terminator character (usually a
newline) appended, rather than a separator placed between entries.
This means that the final entry of a single-line format will be properly
terminated with a new line, just as the "oneline" format does.
For example:
+
---------------------
$ git log -2 --pretty=format:%h 4da45bef \
  | perl -pe '$_ .= " -- NO NEWLINE\n" unless /\n/'
4da45be
7134973 -- NO NEWLINE

$ git log -2 --pretty=tformat:%h 4da45bef \
  | perl -pe '$_ .= " -- NO NEWLINE\n" unless /\n/'
4da45be
7134973
---------------------
+
In addition, any unrecognized string that has a `%` in it is interpreted
as if it has `tformat:` in front of it.  For example, these two are
equivalent:
+
---------------------
$ git log -2 --pretty=tformat:%h 4da45bef
$ git log -2 --pretty=%h 4da45bef
---------------------


COMMON DIFF OPTIONS
-------------------

:git-log: 1
// 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.

:git-diff-core: 1


-p::
-u::
--patch::
	Generate patch (see section on generating patches).
	{git-diff? This is the default.}

-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.
	Implies `-p`.

--raw::
	Generate the raw format.
	{git-diff-core? This is the default.}

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

--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 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.

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


-z::
	When `--raw`, `--numstat`, `--name-only` or `--name-status` has been
	given, do not munge pathnames and use NULs as output field terminators.
+
Without this option, 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 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`.

--no-color::
	Turn off colored 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
gitattributes[1] or git-config[1].  Giving it explicitly
overrides any diff driver or configuration setting.  Diff drivers
override configuration settings.

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

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

--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.

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

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

--find-copies-harder::
	For performance reasons, by default, `-C` option finds copies only
	if the original file of the copy was modified in the same
	changeset.  This flag makes the command
	inspect unmodified files as candidates for the source of
	copy.  This is a very expensive operation for large
	projects, so use it with caution.  Giving more than one
	`-C` option has the same effect.

-D::
--irreversible-delete::
	Omit the preimage for deletes, i.e. print only the header but not
	the diff between the preimage and `/dev/null`. The resulting patch
	is not meant to be applied with `patch` or `git apply`; this is
	solely for people who want to just concentrate on reviewing the
	text after the change. In addition, the output obviously 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.

--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 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.

-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 git-config[1]).  To cancel `diff.orderfile`,
	use `-O/dev/null`.

-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.

-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.

--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`.

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

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

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

--ignore-submodules[=<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 git-config[1] or gitmodules[5]. When
	"untracked" is used submodules are not considered dirty when they only
	contain untracked content (but they are still scanned for modified
	content). Using "dirty" ignores all changes to the work tree of submodules,
	only changes to the commits stored in the superproject are shown (this was
	the behavior until 1.7.0). Using "all" hides all changes to submodules.

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

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

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

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


Generating patches with -p
--------------------------

When "git-diff-index", "git-diff-tree", or "git-diff-files" are run
with a '-p' option, "git diff" without the '--raw' option, or
"git log" with the "-p" option, they
do not produce the output described above; instead they produce a
patch file.  You can customize the creation of such patches via the
GIT_EXTERNAL_DIFF and the GIT_DIFF_OPTS environment variables.

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

1.   It is preceded with a "git diff" header that looks like this:

       diff --git a/file1 b/file2
+
The `a/` and `b/` filenames are the same unless rename/copy is
involved.  Especially, even for a creation or a deletion,
`/dev/null` is _not_ used in place of the `a/` or `b/` filenames.
+
When 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 rename/copy produces, respectively.

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

       old mode <mode>
       new mode <mode>
       deleted file mode <mode>
       new file mode <mode>
       copy from <path>
       copy to <path>
       rename from <path>
       rename to <path>
       similarity index <number>
       dissimilarity index <number>
       index <hash>..<hash> <mode>
+
File modes are printed as 6-digit octal numbers including the file type
and file permission bits.
+
Path names in extended headers do not include the `a/` and `b/` prefixes.
+
The similarity index is the percentage of unchanged lines, and
the dissimilarity index is the percentage of changed lines.  It
is a rounded down integer, followed by a percent sign.  The
similarity index value of 100% is thus reserved for two equal
files, while 100% dissimilarity means that no line from the old
file made it into the new one.
+
The index line includes the SHA-1 checksum before and after the change.
The <mode> is included if the file mode does not change; otherwise,
separate lines indicate the old and the new mode.

3.  TAB, LF, double quote and backslash characters in pathnames
    are represented as `\t`, `\n`, `\"` and `\\`, respectively.
    If there is need for such substitution then the whole
    pathname is put in double quotes.

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

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


combined diff format
--------------------

Any diff-generating command can take the `-c` or `--cc` option to
produce a 'combined diff' when showing a merge. This is the default
format when showing merges with git-diff[1] or
git-show[1]. Note also that you can give the `-m' option to any
of these commands to force generation of diffs with individual parents
of a merge.

A 'combined diff' format looks like this:

------------
diff --combined describe.c
index fabadb8,cc95eb0..4866510
--- a/describe.c
+++ b/describe.c
@@@ -98,20 -98,12 +98,20 @@@
	return (a_date > b_date) ? -1 : (a_date == b_date) ? 0 : 1;
  }

- static void describe(char *arg)
 -static void describe(struct commit *cmit, int last_one)
++static void describe(char *arg, int last_one)
  {
 +	unsigned char sha1[20];
 +	struct commit *cmit;
	struct commit_list *list;
	static int initialized = 0;
	struct commit_name *n;

 +	if (get_sha1(arg, sha1) < 0)
 +		usage(describe_usage);
 +	cmit = lookup_commit_reference(sha1);
 +	if (!cmit)
 +		usage(describe_usage);
 +
	if (!initialized) {
		initialized = 1;
		for_each_ref(get_name);
------------

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

       diff --combined file
+
or like this (when '--cc' option is used):

       diff --cc file

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

       index <hash>,<hash>..<hash>
       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 contents movement (renames and
copying detection) are designed to work with diff of two
<tree-ish> and are not used by combined diff format.

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

       --- a/file
       +++ b/file
+
Similar to two-line header for traditional 'unified' diff
format, `/dev/null` is used to signal created or deleted
files.

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

       @@@ <from-file-range> <from-file-range> <to-file-range> @@@
+
There are (number of parents + 1) `@` characters in the chunk
header for combined diff format.

Unlike the traditional 'unified' diff format, which shows two
files A and B with a single column that has `-` (minus --
appears in A but removed in B), `+` (plus -- missing in A but
added to B), or `" "` (space -- unchanged) prefix, this format
compares two or more files file1, file2,... with one file X, and
shows how X differs from each of fileN.  One column for each of
fileN is prepended to the output line to note how X's line is
different from it.

A `-` character in the column N means that the line appears in
fileN but it does not appear in the result.  A `+` character
in the column N means that the line appears in the result,
and fileN does not have that line (in other words, the line was
added, from the point of view of that parent).

In the above example output, the function signature was changed
from both files (hence two `-` removals from both file1 and
file2, plus `++` to mean one line that was added does not appear
in either file1 or file2).  Also eight other lines are the same
from file1 but do not appear in file2 (hence prefixed with `+`).

When shown by `git diff-tree -c`, it compares the parents of a
merge commit with the merge result (i.e. file1..fileN are the
parents).  When shown by `git diff-files -c`, it compares the
two unresolved merge parents with the working tree file
(i.e. file1 is stage 2 aka "our version", file2 is stage 3 aka
"their version").


EXAMPLES
--------
`git log --no-merges`::

	Show the whole commit history, but skip any merges

`git log v2.6.12.. include/scsi drivers/scsi`::

	Show all commits since version 'v2.6.12' that changed any file
	in the `include/scsi` or `drivers/scsi` subdirectories

`git log --since="2 weeks ago" -- gitk`::

	Show the changes during the last two weeks to the file 'gitk'.
	The ``--'' is necessary to avoid confusion with the *branch* named
	'gitk'

`git log --name-status release..test`::

	Show the commits that are in the "test" branch but not yet
	in the "release" branch, along with the list of paths
	each commit modifies.

`git log --follow builtin/rev-list.c`::

	Shows the commits that changed `builtin/rev-list.c`, including
	those commits that occurred before the file was given its
	present name.

`git log --branches --not --remotes=origin`::

	Shows all commits that are in any of local branches but not in
	any of remote-tracking branches for 'origin' (what you have that
	origin doesn't).

`git log master --not --remotes=*/master`::

	Shows all commits that are in local master but not in any remote
	repository master branches.

`git log -p -m --first-parent`::

	Shows the history including change diffs, but only from the
	``main branch'' perspective, skipping commits that come from merged
	branches, and showing full diffs of changes introduced by the merges.
	This makes sense only when following a strict policy of merging all
	topic branches when staying on a single integration branch.

`git log -L '/int main/',/^}/:main.c`::

	Shows how the function `main()` in the file `main.c` evolved
	over time.

`git log -3`::

	Limits the number of commits to show to 3.

DISCUSSION
----------

At the core level, Git is character encoding agnostic.

 - The pathnames recorded in the index and in the tree objects
   are treated as uninterpreted sequences of non-NUL bytes.
   What readdir(2) returns are what are recorded and compared
   with the data Git keeps track of, which in turn are expected
   to be what lstat(2) and creat(2) accepts.  There is no such
   thing as pathname encoding translation.

 - The contents of the blob objects are uninterpreted sequences
   of bytes.  There is no encoding translation at the core
   level.

 - The commit log messages are uninterpreted sequences of non-NUL
   bytes.

Although we encourage that the commit log messages are encoded
in UTF-8, both the core and Git Porcelain are designed not to
force UTF-8 on projects.  If all participants of a particular
project find it more convenient to use legacy encodings, Git
does not forbid it.  However, there are a few things to keep in
mind.

. 'git commit' and 'git commit-tree' issues
  a warning if the commit log message given to it does not look
  like a valid UTF-8 string, unless you explicitly say your
  project uses a legacy encoding.  The way to say this is to
  have i18n.commitencoding in `.git/config` file, like this:
+
------------
[i18n]
	commitencoding = ISO-8859-1
------------
+
Commit objects created with the above setting record the value
of `i18n.commitencoding` in its `encoding` header.  This is to
help other people who look at them later.  Lack of this header
implies that the commit log message is encoded in UTF-8.

. 'git log', 'git show', 'git blame' and friends look at the
  `encoding` header of a commit object, and try to re-code the
  log message into UTF-8 unless otherwise specified.  You can
  specify the desired output encoding with
  `i18n.logoutputencoding` in `.git/config` file, like this:
+
------------
[i18n]
	logoutputencoding = ISO-8859-1
------------
+
If you do not have this configuration variable, the value of
`i18n.commitencoding` is used instead.

Note that we deliberately chose not to re-code the commit log
message when a commit is made to force UTF-8 at the commit
object level, because re-coding to UTF-8 is not necessarily a
reversible operation.


CONFIGURATION
-------------

See git-config[1] for core variables and git-diff[1]
for settings related to diff generation.

format.pretty::
	Default for the `--format` option.  (See 'Pretty Formats' above.)
	Defaults to `medium`.

i18n.logOutputEncoding::
	Encoding to use when displaying logs.  (See 'Discussion' above.)
	Defaults to the value of `i18n.commitEncoding` if set, and UTF-8
	otherwise.

log.date::
	Default format for human-readable dates.  (Compare the
	`--date` option.)  Defaults to "default", which means to write
	dates like `Sat May 8 19:35:34 2010 -0500`.

log.showroot::
	If `false`, `git log` and related commands will not treat the
	initial commit as a big creation event.  Any root commits in
	`git log -p` output would be shown without a diff attached.
	The default is `true`.

mailmap.*::
	See git-shortlog[1].

notes.displayRef::
	Which refs, in addition to the default set by `core.notesRef`
	or 'GIT_NOTES_REF', to read notes from when showing commit
	messages with the `log` family of commands.  See
	git-notes[1].
+
May be an unabbreviated ref name or a glob and may be specified
multiple times.  A warning will be issued for refs that do not exist,
but a glob that does not match any refs is silently ignored.
+
This setting can be disabled by the `--no-notes` option,
overridden by the 'GIT_NOTES_DISPLAY_REF' environment variable,
and overridden by the `--notes=<ref>` option.

GIT
---
Part of the git[1] suite