GIT-BLAME(1) Git Manual GIT-BLAME(1)NAMEgit-blame - Show what revision and author last modified each line of a
file
SYNOPSISgit-blame [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-p] [-w] [--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 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-b Show blank SHA-1 for boundary commits. This can also be
controlled via the blame.blankboundary config option.
--root Do not treat root commits as boundaries. This can also be
controlled via the blame.showroot config option.
--show-stats
Include additional statistics at the end of blame output.
-L <start>,<end>
Annotate only the given line range. <start> and <end> can take
one of these forms:
· number
If <start> or <end> is a number, it specifies an absolute
line number (lines count from 1).
· /regex/
This form will use the first line matching the given POSIX
regex. If <end> is a regex, it will search starting at the
line given by <start>.
· +offset or -offset
This is only valid for <end> and will specify a number of
lines before or after the line given by <start>.
-l Show long rev (Default: off).
-t Show raw timestamp (Default: off).
-S <revs-file>
Use revs from revs-file instead of calling git-rev-list(1).
-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 the named file (specify - to make the command read from the
standard input).
-M|<num>|
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.
<num> is optional but it is the lower bound on the number of
alphanumeric characters that git must detect as moving within a
file for it to associate those lines with the parent commit.
-C|<num>|
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.
<num> is optional but it is the lower bound on the number of
alphanumeric characters that git must detect as moving between
files for it to associate those lines with the parent commit.
-h, --help
Show help message.
-c Use the same output mode as git-annotate(1) (Default: off).
--score-debug
Include debugging information related to the movement of lines
between files (see -C) and lines moved within a file (see -M).
The first number listed is the score. This is the number of
alphanumeric characters detected to be moved between or within
files. This must be above a certain threshold for git-blame to
consider those lines of code to have been moved.
-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).
-s Suppress author name and timestamp from the output.
-w Ignore whitespace when comparing parent's version and child's to
find where the lines came from.
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^! 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.
1. Each blame entry always starts with a line of:
<40-byte hex sha1> <sourceline> <resultline> <num_lines>
Line numbers count from 1.
2. 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).
3. 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 ALSOgit-annotate(1)AUTHOR
Written by Junio C Hamano <junkio@cox.net>
GIT
Part of the git(7) suite
Git 1.5.5.2 10/21/2008 GIT-BLAME(1)
