Documentation/git-blame.txt - jrn/git - Git at Google

 git-blame(1)
 ============

 NAME
 ----
 git-blame - Show what revision and author last modified each line of a file

 SYNOPSIS
 --------
 [verse]
 'git-blame' [-c] [-l] [-t] [-f] [-n] [-p] [--incremental] [-L n,m] [-S <revs-file>]
             [-M] [-C] [-C] [--since=<date>] [<rev> | --contents <file>] [--] <file>

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

 Annotates each line in the given file with information from the revision which
 last modified the line. Optionally, start annotating from the given revision.

 Also it can limit the range of lines annotated.

 This report doesn't tell you anything about lines which have been deleted or
 replaced; you need to use a tool such as gitlink:git-diff[1] or the "pickaxe"
 interface briefly mentioned in the following paragraph.

 Apart from supporting file annotation, git also supports searching the
 development history for when a code snippet occurred in a change. This makes it
 possible to track when a code snippet was added to a file, moved or copied
 between files, and eventually deleted or replaced. It works by searching for
 a text string in the diff. A small example:

 -----------------------------------------------------------------------------
 $ git log --pretty=oneline -S'blame_usage'
 5040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file>
 ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output
 -----------------------------------------------------------------------------

 OPTIONS
 -------
 -c, --compatibility::
 	Use the same output mode as gitlink:git-annotate[1] (Default: off).

 -L n,m::
 	Annotate only the specified line range (lines count from 1).

 -l, --long::
 	Show long rev (Default: off).

 -t, --time::
 	Show raw timestamp (Default: off).

 -S, --rev-file <revs-file>::
 	Use revs from revs-file instead of calling gitlink:git-rev-list[1].

 -f, --show-name::
 	Show filename in the original commit.  By default
 	filename is shown if there is any line that came from a
 	file with different name, due to rename detection.

 -n, --show-number::
 	Show line number in the original commit (Default: off).

 -p, --porcelain::
 	Show in a format designed for machine consumption.

 --incremental::
 	Show the result incrementally in a format designed for
 	machine consumption.

 --contents <file>::
 	When <rev> is not specified, the command annotates the
 	changes starting backwards from the working tree copy.
 	This flag makes the command pretend as if the working
 	tree copy has the contents of he named file (specify
 	`-` to make the command read from the standard input).

 -M::
 	Detect moving lines in the file as well.  When a commit
 	moves a block of lines in a file (e.g. the original file
 	has A and then B, and the commit changes it to B and
 	then A), traditional 'blame' algorithm typically blames
 	the lines that were moved up (i.e. B) to the parent and
 	assigns blame to the lines that were moved down (i.e. A)
 	to the child commit.  With this option, both groups of
 	lines are blamed on the parent.

 -C::
 	In addition to `-M`, detect lines copied from other
 	files that were modified in the same commit.  This is
 	useful when you reorganize your program and move code
 	around across files.  When this option is given twice,
 	the command looks for copies from all other files in the
 	parent for the commit that creates the file in addition.

 -h, --help::
 	Show help message.


 THE PORCELAIN FORMAT
 --------------------

 In this format, each line is output after a header; the
 header at the minimum has the first line which has:

 - 40-byte SHA-1 of the commit the line is attributed to;
 - the line number of the line in the original file;
 - the line number of the line in the final file;
 - on a line that starts a group of line from a different
   commit than the previous one, the number of lines in this
   group.  On subsequent lines this field is absent.

 This header line is followed by the following information
 at least once for each commit:

 - author name ("author"), email ("author-mail"), time
   ("author-time"), and timezone ("author-tz"); similarly
   for committer.
 - filename in the commit the line is attributed to.
 - the first line of the commit log message ("summary").

 The contents of the actual line is output after the above
 header, prefixed by a TAB. This is to allow adding more
 header elements later.


 SPECIFYING RANGES
 -----------------

 Unlike `git-blame` and `git-annotate` in older git, the extent
 of annotation can be limited to both line ranges and revision
 ranges.  When you are interested in finding the origin for
 ll. 40-60 for file `foo`, you can use `-L` option like these
 (they mean the same thing -- both ask for 21 lines starting at
 line 40):

 	git blame -L 40,60 foo
 	git blame -L 40,+21 foo

 Also you can use regular expression to specify the line range.

 	git blame -L '/^sub hello {/,/^}$/' foo

 would limit the annotation to the body of `hello` subroutine.

 When you are not interested in changes older than the version
 v2.6.18, or changes older than 3 weeks, you can use revision
 range specifiers  similar to `git-rev-list`:

 	git blame v2.6.18.. -- foo
 	git blame --since=3.weeks -- foo

 When revision range specifiers are used to limit the annotation,
 lines that have not changed since the range boundary (either the
 commit v2.6.18 or the most recent commit that is more than 3
 weeks old in the above example) are blamed for that range
 boundary commit.

 A particularly useful way is to see if an added file have lines
 created by copy-and-paste from existing files.  Sometimes this
 indicates that the developer was being sloppy and did not
 refactor the code properly.  You can first find the commit that
 introduced the file with:

 	git log --diff-filter=A --pretty=short -- foo

 and then annotate the change between the commit and its
 parents, using `commit{caret}!` notation:

 	git blame -C -C -f $commit^! -- foo


 INCREMENTAL OUTPUT
 ------------------

 When called with `--incremental` option, the command outputs the
 result as it is built.  The output generally will talk about
 lines touched by more recent commits first (i.e. the lines will
 be annotated out of order) and is meant to be used by
 interactive viewers.

 The output format is similar to the Porcelain format, but it
 does not contain the actual lines from the file that is being
 annotated.

 . Each blame entry always starts with a line of:

 	<40-byte hex sha1> <sourceline> <resultline> <num_lines>
 +
 Line numbers count from 1.

 . The first time that commit shows up in the stream, it has various
   other information about it printed out with a one-word tag at the
   beginning of each line about that "extended commit info" (author,
   email, committer, dates, summary etc).

 . Unlike Porcelain format, the filename information is always
   given and terminates the entry:

 	"filename" <whitespace-quoted-filename-goes-here>
 +
 and thus it's really quite easy to parse for some line- and word-oriented
 parser (which should be quite natural for most scripting languages).
 +
 [NOTE]
 For people who do parsing: to make it more robust, just ignore any
 lines in between the first and last one ("<sha1>" and "filename" lines)
 where you don't recognize the tag-words (or care about that particular
 one) at the beginning of the "extended information" lines. That way, if
 there is ever added information (like the commit encoding or extended
 commit commentary), a blame viewer won't ever care.


 SEE ALSO
 --------
 gitlink:git-annotate[1]

 AUTHOR
 ------
 Written by Junio C Hamano <junkio@cox.net>

 GIT
 ---
 Part of the gitlink:git[7] suite
	git-blame(1)
	============

	NAME
	----
	git-blame - Show what revision and author last modified each line of a file

	SYNOPSIS
	--------
	[verse]
	'git-blame' [-c] [-l] [-t] [-f] [-n] [-p] [--incremental] [-L n,m] [-S <revs-file>]
	[-M] [-C] [-C] [--since=<date>] [<rev> \| --contents <file>] [--] <file>

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

	Annotates each line in the given file with information from the revision which
	last modified the line. Optionally, start annotating from the given revision.

	Also it can limit the range of lines annotated.

	This report doesn't tell you anything about lines which have been deleted or
	replaced; you need to use a tool such as gitlink:git-diff[1] or the "pickaxe"
	interface briefly mentioned in the following paragraph.

	Apart from supporting file annotation, git also supports searching the
	development history for when a code snippet occurred in a change. This makes it
	possible to track when a code snippet was added to a file, moved or copied
	between files, and eventually deleted or replaced. It works by searching for
	a text string in the diff. A small example:

	-----------------------------------------------------------------------------
	$ git log --pretty=oneline -S'blame_usage'
	5040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file>
	ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output
	-----------------------------------------------------------------------------

	OPTIONS
	-------
	-c, --compatibility::
	Use the same output mode as gitlink:git-annotate[1] (Default: off).

	-L n,m::
	Annotate only the specified line range (lines count from 1).

	-l, --long::
	Show long rev (Default: off).

	-t, --time::
	Show raw timestamp (Default: off).

	-S, --rev-file <revs-file>::
	Use revs from revs-file instead of calling gitlink:git-rev-list[1].

	-f, --show-name::
	Show filename in the original commit. By default
	filename is shown if there is any line that came from a
	file with different name, due to rename detection.

	-n, --show-number::
	Show line number in the original commit (Default: off).

	-p, --porcelain::
	Show in a format designed for machine consumption.

	--incremental::
	Show the result incrementally in a format designed for
	machine consumption.

	--contents <file>::
	When <rev> is not specified, the command annotates the
	changes starting backwards from the working tree copy.
	This flag makes the command pretend as if the working
	tree copy has the contents of he named file (specify
	`-` to make the command read from the standard input).

	-M::
	Detect moving lines in the file as well. When a commit
	moves a block of lines in a file (e.g. the original file
	has A and then B, and the commit changes it to B and
	then A), traditional 'blame' algorithm typically blames
	the lines that were moved up (i.e. B) to the parent and
	assigns blame to the lines that were moved down (i.e. A)
	to the child commit. With this option, both groups of
	lines are blamed on the parent.

	-C::
	In addition to `-M`, detect lines copied from other
	files that were modified in the same commit. This is
	useful when you reorganize your program and move code
	around across files. When this option is given twice,
	the command looks for copies from all other files in the
	parent for the commit that creates the file in addition.

	-h, --help::
	Show help message.


	THE PORCELAIN FORMAT
	--------------------

	In this format, each line is output after a header; the
	header at the minimum has the first line which has:

	- 40-byte SHA-1 of the commit the line is attributed to;
	- the line number of the line in the original file;
	- the line number of the line in the final file;
	- on a line that starts a group of line from a different
	commit than the previous one, the number of lines in this
	group. On subsequent lines this field is absent.

	This header line is followed by the following information
	at least once for each commit:

	- author name ("author"), email ("author-mail"), time
	("author-time"), and timezone ("author-tz"); similarly
	for committer.
	- filename in the commit the line is attributed to.
	- the first line of the commit log message ("summary").

	The contents of the actual line is output after the above
	header, prefixed by a TAB. This is to allow adding more
	header elements later.


	SPECIFYING RANGES
	-----------------

	Unlike `git-blame` and `git-annotate` in older git, the extent
	of annotation can be limited to both line ranges and revision
	ranges. When you are interested in finding the origin for
	ll. 40-60 for file `foo`, you can use `-L` option like these
	(they mean the same thing -- both ask for 21 lines starting at
	line 40):

	git blame -L 40,60 foo
	git blame -L 40,+21 foo

	Also you can use regular expression to specify the line range.

	git blame -L '/^sub hello {/,/^}$/' foo

	would limit the annotation to the body of `hello` subroutine.

	When you are not interested in changes older than the version
	v2.6.18, or changes older than 3 weeks, you can use revision
	range specifiers similar to `git-rev-list`:

	git blame v2.6.18.. -- foo
	git blame --since=3.weeks -- foo

	When revision range specifiers are used to limit the annotation,
	lines that have not changed since the range boundary (either the
	commit v2.6.18 or the most recent commit that is more than 3
	weeks old in the above example) are blamed for that range
	boundary commit.

	A particularly useful way is to see if an added file have lines
	created by copy-and-paste from existing files. Sometimes this
	indicates that the developer was being sloppy and did not
	refactor the code properly. You can first find the commit that
	introduced the file with:

	git log --diff-filter=A --pretty=short -- foo

	and then annotate the change between the commit and its
	parents, using `commit{caret}!` notation:

	git blame -C -C -f $commit^! -- foo


	INCREMENTAL OUTPUT
	------------------

	When called with `--incremental` option, the command outputs the
	result as it is built. The output generally will talk about
	lines touched by more recent commits first (i.e. the lines will
	be annotated out of order) and is meant to be used by
	interactive viewers.

	The output format is similar to the Porcelain format, but it
	does not contain the actual lines from the file that is being
	annotated.

	. Each blame entry always starts with a line of:

	<40-byte hex sha1> <sourceline> <resultline> <num_lines>
	+
	Line numbers count from 1.

	. The first time that commit shows up in the stream, it has various
	other information about it printed out with a one-word tag at the
	beginning of each line about that "extended commit info" (author,
	email, committer, dates, summary etc).

	. Unlike Porcelain format, the filename information is always
	given and terminates the entry:

	"filename" <whitespace-quoted-filename-goes-here>
	+
	and thus it's really quite easy to parse for some line- and word-oriented
	parser (which should be quite natural for most scripting languages).
	+
	[NOTE]
	For people who do parsing: to make it more robust, just ignore any
	lines in between the first and last one ("<sha1>" and "filename" lines)
	where you don't recognize the tag-words (or care about that particular
	one) at the beginning of the "extended information" lines. That way, if
	there is ever added information (like the commit encoding or extended
	commit commentary), a blame viewer won't ever care.


	SEE ALSO
	--------
	gitlink:git-annotate[1]

	AUTHOR
	------
	Written by Junio C Hamano <junkio@cox.net>

	GIT
	---
	Part of the gitlink:git[7] suite