Documentation/git-format-rev.adoc - git - Git at Google

 git-format-rev(1)
 =================

 NAME
 ----
 git-format-rev - EXPERIMENTAL: Pretty format revisions on demand


 SYNOPSIS
 --------
 [synopsis]
 (EXPERIMENTAL!) git format-rev --stdin-mode=<mode> --format=<pretty> [--[no-]notes=<ref>] [-z] [--[no-]null-output] [--[no-]null-input]

 DESCRIPTION
 -----------

 Pretty format revisions from standard input.

 THIS COMMAND IS EXPERIMENTAL. THE BEHAVIOR MAY CHANGE.

 OPTIONS
 -------

 `--stdin-mode=<mode>`::
 	How to interpret standard input data:
 +
 --
 `revs`;; Each line or record (see the <<io,INPUT AND OUTPUT FORMATS>>
 	section) is interpreted as a commit. Any kind of revision
 	expression can be used (see linkgit:gitrevisions[7]). Annotated
 	tags are peeled (see linkgit:gitglossary[7]).
 +
 The argument `rev` is also accepted.

 `text`;; Formats all commit object names found in freeform text. These
 	must the full object names, i.e. abbreviated hexidecimal object
 	names will not be interpreted.
 +
 Anything that is parsed as an object name but that is not found to be a
 commit object name is left alone (echoed).
 --

 `--format=<pretty>`::
 	Pretty format string.

 `--notes=<ref>`::
 `--no-notes`::
 	Custom notes ref. Notes are displayed when using the `%N`
 	atom. See linkgit:git-notes[1].

 `-z`::
 `--null`::
 	Use _NUL_ character to terminate both input and output instead
 	of newline. This option cannot be negated.
 +
 This is useful if both the input and output could contain newlines or if
 the input to this command also uses _NUL_ character termination; see the
 <<io,INPUT AND OUTPUT FORMATS>> section below.
 +
 The mode `--stdin-mode=text` can have use for this option when it needs
 to process input like for example `git last-modified -z`; see the
 <<examples,EXAMPLES>> section below.

 `--null-output`::
 `--no-null-output`::
 	Use _NUL_ character to terminate output instead of newline. The
 	default is `--no-null-output`.
 +
 This is useful if the output could contain newlines, for example if the
 `%n` (newline) atom is used.

 `--null-input`::
 `--no-null-input`::
 	Use _NUL_ character to terminate input instead of newline. The
 	default is `--no-null-input`.
 +
 This is useful if the input revision expressions could contain newlines.

 [[io]]
 INPUT AND OUTPUT FORMAT
 -----------------------

 The command uses newlines for both input and output termination by
 default. See the `-z`, `--null-output`, and `--null-input` options for
 using _NUL_ character as the terminator.

 The mode `--stdin-mode=revs` outputs one formatted commit followed by
 the terminator. This could either be called a _line_ or a _record_ in
 case "line" is too suggestive of newline termination.

 Note that this means that the terminator character (newline or _NUL_)
 acts as a _terminator_, not a _separator_. In other words, the final
 line or record is also terminated by the terminator character.

 The mode `--stdin-mode=text` replaces each object name with the
 formatted commit, i.e. the format `%s` would transform some commit
 object name to `<subject>` without any termination. Like this:

 ----
 Did we not fix this in "<subject>"?
 ----

 It is safe to interactively read and write from this command since each
 record is immediately flushed.

 [[examples]]
 EXAMPLES
 --------

 The command linkgit:git-last-modified[1] shows the commit that each file
 was last modified in.

 ----
 $ git last-modified -- README.md Makefile
 7798034171030be0909c56377a4e0e10e6d2df93	Makefile
 c50fbb2dd225e7e82abba4380423ae105089f4d7	README.md
 ----

 We can pipe the result to this command in order to replace the object
 name with the commit author.

 ----
 $ git last-modified -- README.md Makefile |
     git format-rev --stdin-mode=text --format=%an
 Junio C Hamano	Makefile
 Todd Zullinger	README.md
 ----

 Another example is _formatting commits in commit messages_. Given this commit message:

 ----
 Fix off-by-one error

 Fix off-by-one error introduced in
 e83c5163316f89bfbde7d9ab23ca2e25604af290.

 We thought we fixed this in 5569bf9bbedd63a00780fc5c110e0cfab3aa97b9 but
 that only covered 1/3 of the faulty cases.
 ----

 We can format the commits and use par(1) to reflow the text, say in a
 `commit-msg` hook:

 ----
 $ git config set hook.reference-commits.event commit-msg
 $ git config set hook.reference-commits.command reference-commits
 $ cat $(which reference-commits)
 #/bin/sh

 msg="$1"
 rewritten=$(mktemp)
 git format-rev --stdin-mode=text --format=reference <"$msg" |
     par >"$rewritten"
 mv "$rewritten" "$msg"
 ----

 Which will produce something like this:

 ----
 Fix off-by-one error

 Fix off-by-one error introduced in e83c5163316 (Implement better memory
 allocator, 2005-04-07).

 We thought we fixed this in 5569bf9bbed (Fix memory allocator,
 2005-06-22) but that only covered 1/3 of the faulty cases.
 ----

 DISCUSSION
 ----------

 This command lets you format any number of revisions in any order
 through one command invocation. Consider the
 linkgit:git-last-modified[1] case from the <<examples,EXAMPLES>> section
 above:

 1. There might be hundreds of files
 2. Commits can be repeated, i.e. two or more files were last modified in
    the same commit

 Two widely-used commands which pretty formats commits are
 linkgit:git-log[1] and linkgit:git-show[1]. It turns out that they are
 not a good fit for the above use case.

 - The output of linkgit:git-last-modified[1] would have to be processed
   in stages since you need to transform the first column separately and
   then link the author to the filename. But this is surmountable.
 - You can feed each commit to `git show` or `git log --no-walk -1`. But
   that means that you need to create a process for each line.
 - Let’s say that you want to use one process, not one per line. So you
   want to feed all the commits to the command. Now you face the problem
   that you have to feed all the commits to the commands before you get
   any output (this is also the case for the `--stdin` modes). In other
   words, you cannot loop through each line, get the author for the
   commit, and output the author and the filename. You need to feed all
   the commits, get back all the output, and match the output with the
   filename.
 - But the next problem is that commands will deduplicate the input and
   only output one commit one single time only. Thus you cannot make the
   output order match the input order, since a commit could have been
   repeated in the original input.

 In short, it is straightforward to use these two commands if you use one
 process per line. It is much more work if you just want to use one
 process, but still doable. In contrast, this problem is solved with just
 another shell pipeline with this command.

 SEE ALSO
 --------
 linkgit:git-name-rev[1],
 linkgit:git-log[1].

 GIT
 ---
 Part of the linkgit:git[1] suite
	git-format-rev(1)
	=================

	NAME
	----
	git-format-rev - EXPERIMENTAL: Pretty format revisions on demand


	SYNOPSIS
	--------
	[synopsis]
	(EXPERIMENTAL!) git format-rev --stdin-mode=<mode> --format=<pretty> [--[no-]notes=<ref>] [-z] [--[no-]null-output] [--[no-]null-input]

	DESCRIPTION
	-----------

	Pretty format revisions from standard input.

	THIS COMMAND IS EXPERIMENTAL. THE BEHAVIOR MAY CHANGE.

	OPTIONS
	-------

	`--stdin-mode=<mode>`::
	How to interpret standard input data:
	+
	--
	`revs`;; Each line or record (see the <<io,INPUT AND OUTPUT FORMATS>>
	section) is interpreted as a commit. Any kind of revision
	expression can be used (see linkgit:gitrevisions[7]). Annotated
	tags are peeled (see linkgit:gitglossary[7]).
	+
	The argument `rev` is also accepted.

	`text`;; Formats all commit object names found in freeform text. These
	must the full object names, i.e. abbreviated hexidecimal object
	names will not be interpreted.
	+
	Anything that is parsed as an object name but that is not found to be a
	commit object name is left alone (echoed).
	--

	`--format=<pretty>`::
	Pretty format string.

	`--notes=<ref>`::
	`--no-notes`::
	Custom notes ref. Notes are displayed when using the `%N`
	atom. See linkgit:git-notes[1].

	`-z`::
	`--null`::
	Use _NUL_ character to terminate both input and output instead
	of newline. This option cannot be negated.
	+
	This is useful if both the input and output could contain newlines or if
	the input to this command also uses _NUL_ character termination; see the
	<<io,INPUT AND OUTPUT FORMATS>> section below.
	+
	The mode `--stdin-mode=text` can have use for this option when it needs
	to process input like for example `git last-modified -z`; see the
	<<examples,EXAMPLES>> section below.

	`--null-output`::
	`--no-null-output`::
	Use _NUL_ character to terminate output instead of newline. The
	default is `--no-null-output`.
	+
	This is useful if the output could contain newlines, for example if the
	`%n` (newline) atom is used.

	`--null-input`::
	`--no-null-input`::
	Use _NUL_ character to terminate input instead of newline. The
	default is `--no-null-input`.
	+
	This is useful if the input revision expressions could contain newlines.

	[[io]]
	INPUT AND OUTPUT FORMAT
	-----------------------

	The command uses newlines for both input and output termination by
	default. See the `-z`, `--null-output`, and `--null-input` options for
	using _NUL_ character as the terminator.

	The mode `--stdin-mode=revs` outputs one formatted commit followed by
	the terminator. This could either be called a _line_ or a _record_ in
	case "line" is too suggestive of newline termination.

	Note that this means that the terminator character (newline or _NUL_)
	acts as a _terminator_, not a _separator_. In other words, the final
	line or record is also terminated by the terminator character.

	The mode `--stdin-mode=text` replaces each object name with the
	formatted commit, i.e. the format `%s` would transform some commit
	object name to `<subject>` without any termination. Like this:

	----
	Did we not fix this in "<subject>"?
	----

	It is safe to interactively read and write from this command since each
	record is immediately flushed.

	[[examples]]
	EXAMPLES
	--------

	The command linkgit:git-last-modified[1] shows the commit that each file
	was last modified in.

	----
	$ git last-modified -- README.md Makefile
	7798034171030be0909c56377a4e0e10e6d2df93 Makefile
	c50fbb2dd225e7e82abba4380423ae105089f4d7 README.md
	----

	We can pipe the result to this command in order to replace the object
	name with the commit author.

	----
	$ git last-modified -- README.md Makefile \|
	git format-rev --stdin-mode=text --format=%an
	Junio C Hamano Makefile
	Todd Zullinger README.md
	----

	Another example is _formatting commits in commit messages_. Given this commit message:

	----
	Fix off-by-one error

	Fix off-by-one error introduced in
	e83c5163316f89bfbde7d9ab23ca2e25604af290.

	We thought we fixed this in 5569bf9bbedd63a00780fc5c110e0cfab3aa97b9 but
	that only covered 1/3 of the faulty cases.
	----

	We can format the commits and use par(1) to reflow the text, say in a
	`commit-msg` hook:

	----
	$ git config set hook.reference-commits.event commit-msg
	$ git config set hook.reference-commits.command reference-commits
	$ cat $(which reference-commits)
	#/bin/sh

	msg="$1"
	rewritten=$(mktemp)
	git format-rev --stdin-mode=text --format=reference <"$msg" \|
	par >"$rewritten"
	mv "$rewritten" "$msg"
	----

	Which will produce something like this:

	----
	Fix off-by-one error

	Fix off-by-one error introduced in e83c5163316 (Implement better memory
	allocator, 2005-04-07).

	We thought we fixed this in 5569bf9bbed (Fix memory allocator,
	2005-06-22) but that only covered 1/3 of the faulty cases.
	----

	DISCUSSION
	----------

	This command lets you format any number of revisions in any order
	through one command invocation. Consider the
	linkgit:git-last-modified[1] case from the <<examples,EXAMPLES>> section
	above:

	1. There might be hundreds of files
	2. Commits can be repeated, i.e. two or more files were last modified in
	the same commit

	Two widely-used commands which pretty formats commits are
	linkgit:git-log[1] and linkgit:git-show[1]. It turns out that they are
	not a good fit for the above use case.

	- The output of linkgit:git-last-modified[1] would have to be processed
	in stages since you need to transform the first column separately and
	then link the author to the filename. But this is surmountable.
	- You can feed each commit to `git show` or `git log --no-walk -1`. But
	that means that you need to create a process for each line.
	- Let’s say that you want to use one process, not one per line. So you
	want to feed all the commits to the command. Now you face the problem
	that you have to feed all the commits to the commands before you get
	any output (this is also the case for the `--stdin` modes). In other
	words, you cannot loop through each line, get the author for the
	commit, and output the author and the filename. You need to feed all
	the commits, get back all the output, and match the output with the
	filename.
	- But the next problem is that commands will deduplicate the input and
	only output one commit one single time only. Thus you cannot make the
	output order match the input order, since a commit could have been
	repeated in the original input.

	In short, it is straightforward to use these two commands if you use one
	process per line. It is much more work if you just want to use one
	process, but still doable. In contrast, this problem is solved with just
	another shell pipeline with this command.

	SEE ALSO
	--------
	linkgit:git-name-rev[1],
	linkgit:git-log[1].

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