GIT-BLAME(1)GIT-BLAME(1)NAMEgit-blame - Show what revision and author last modified each line of a
file
SYNOPSIS
git blame [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-p] [-w] [--incremental] [-L n,m]
[-S <revs-file>] [-M] [-C] [-C] [-C] [--since=<date>]
[<rev> | --contents <file> | --reverse <rev>] [--] <file>
DESCRIPTION
Annotates each line in the given file with information from the revi-
sion which last modified the line. Optionally, start annotating from
the given revision.
The command can also limit the range of lines annotated.
The report does not tell you anything about lines which have been
deleted or replaced; you need to use a tool such as git diff 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:
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$ git log --pretty=oneline -S'blame_usage'
5040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file>
ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output
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OPTIONS-b Show blank SHA-1 for boundary commits. This can also be con-
trolled via the blame.blankboundary config option.
--root Do not treat root commits as boundaries. This can also be con-
trolled via the blame.showroot config option.
--show-stats
Include additional statistics at the end of blame output.
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GIT-BLAME(1)GIT-BLAME(1)-L <start>,<end>
Annotate only the given line range. <start> and <end> can take
one of these forms:
o number
If <start> or <end> is a number, it specifies an absolute
line number (lines count from 1).
o /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>.
o +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 revisions from revs-file instead of calling git-rev-list(1).
--reverse
Walk history forward instead of backward. Instead of showing the
revision in which a line appeared, this shows the last revision
in which a line has existed. This requires a range of revision
like START..END where the path to blame exists in START.
-p, --porcelain
Show in a format designed for machine consumption.
--incremental
Show the result incrementally in a format designed for machine
consumption.
--encoding=<encoding>
Specifies the encoding used to output author names and commit
summaries. Setting it to none makes blame output unconverted
data. For more information see the discussion about encoding in
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the git-log(1) manual page.
--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).
--date <format>
The value is one of the following alternatives: {rela-
tive,local,default,iso,rfc,short}. If --date is not provided,
the value of the blame.date config variable is used. If the
blame.date config variable is also not set, the iso format is
used. For more information, See the discussion of the --date
option at git-log(1).
-M|<num>|
Detect moved or copied lines within a file. When a commit moves
or copies a block of lines (e.g. the original file has A and
then B, and the commit changes it to B and then A), the tradi-
tional blame algorithm notices only half of the movement and
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 by running extra passes of inspection.
<num> is optional but it is the lower bound on the number of
alphanumeric characters that git must detect as moving/copying
within a file for it to associate those lines with the parent
commit. The default value is 20.
-C|<num>|
In addition to -M, detect lines moved or 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 additionally looks for
copies from other files in the commit that creates the file.
When this option is given three times, the command additionally
looks for copies from other files in any commit.
<num> is optional but it is the lower bound on the number of
alphanumeric characters that git must detect as moving/copying
between files for it to associate those lines with the parent
commit. And the default value is 40. If there are more than one
-C options given, the <num> argument of the last -C will take
effect.
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GIT-BLAME(1)GIT-BLAME(1)-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 as having been 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 the filename in the original commit. By default the file-
name is shown if there is any line that came from a file with a
different name, due to rename detection.
-n, --show-number
Show the line number in the original commit (Default: off).
-s Suppress the author name and timestamp from the output.
-w Ignore whitespace when comparing the parent’s version and
the 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:
o 40-byte SHA-1 of the commit the line is attributed to;
o the line number of the line in the original file;
o the line number of the line in the final file;
o on a line that starts a group of lines 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:
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GIT-BLAME(1)GIT-BLAME(1)
o the author name ("author"), email ("author-mail"), time
("author-time"), and timezone ("author-tz"); similarly for commit-
ter.
o the filename in the commit that the line is attributed to.
o the first line of the commit log message ("summary").
The contents of the actual line is output after the above header, pre-
fixed by a TAB. This is to allow adding more header elements later.
SPECIFYING RANGES
Unlike git blame and git annotate in older versions of git, the extent
of the annotation can be limited to both line ranges and revision
ranges. When you are interested in finding the origin for lines 40-60
for file foo, you can use the -L option like so (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 a regular expression to specify the line range:
git blame -L '/^sub hello {/,/^}$/' foo
which limits the annotation to the body of the hello subroutine.
When you are not interested in changes older than version v2.6.18, or
changes older than 3 weeks, you can use revision range specifiers simi-
lar 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 has 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
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GIT-BLAME(1)GIT-BLAME(1)
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.
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 a 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 describing the extra commit information
(author, email, committer, dates, summary, etc.).
3. Unlike the Porcelain format, the filename information is always
given and terminates the entry:
"filename" <whitespace-quoted-filename-goes-here>
and thus it is really quite easy to parse for some line- and
word-oriented parser (which should be quite natural for most script-
ing languages).
Note
For people who do parsing: to make it more robust, just ignore any
lines between the first and last one ("<sha1>" and "filename" lines)
where you do not recognize the tag words (or care about that partic-
ular 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 will not care.
MAPPING AUTHORS
If the file .mailmap exists at the toplevel of the repository, or at
the location pointed to by the mailmap.file configuration option, it is
used to map author and committer names and email addresses to canonical
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real names and email addresses.
In the simple form, each line in the file consists of the canonical
real name of an author, whitespace, and an email address used in the
commit (enclosed by < and >) to map to the name. For example:
Proper Name <commit@email.xx>
The more complex forms are:
<proper@email.xx> <commit@email.xx>
which allows mailmap to replace only the email part of a commit, and:
Proper Name <proper@email.xx> <commit@email.xx>
which allows mailmap to replace both the name and the email of a commit
matching the specified commit email address, and:
Proper Name <proper@email.xx> Commit Name <commit@email.xx>
which allows mailmap to replace both the name and the email of a commit
matching both the specified commit name and email address.
Example 1: Your history contains commits by two authors, Jane and Joe,
whose names appear in the repository under several forms:
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Joe Developer <joe@example.com>
Joe R. Developer <joe@example.com>
Jane Doe <jane@example.com>
Jane Doe <jane@laptop.(none)>
Jane D. <jane@desktop.(none)>
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Now suppose that Joe wants his middle name initial used, and Jane
prefers her family name fully spelled out. A proper .mailmap file would
look like:
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Jane Doe <jane@desktop.(none)>
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GIT-BLAME(1)GIT-BLAME(1)
Joe R. Developer <joe@example.com>
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Note how there is no need for an entry for <jane@laptop:
mailto:jane@laptop.(none)>, because the real name of that author is
already correct.
Example 2: Your repository contains commits from the following authors:
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nick1 <bugs@company.xx>
nick2 <bugs@company.xx>
nick2 <nick2@company.xx>
santa <me@company.xx>
claus <me@company.xx>
CTO <cto@coompany.xx>
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Then you might want a .mailmap file that looks like:
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<cto@company.xx> <cto@coompany.xx>
Some Dude <some@dude.xx> nick1 <bugs@company.xx>
Other Author <other@author.xx> nick2 <bugs@company.xx>
Other Author <other@author.xx> <nick2@company.xx>
Santa Claus <santa.claus@northpole.xx> <me@company.xx>
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Use hash # for comments that are either on their own line, or after the
email address.
SEE ALSOgit-annotate(1)AUTHOR
Written by Junio C Hamano <gitster@pobox.com: mailto:gitster@pobox.com>
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GIT-BLAME(1)GIT-BLAME(1)GIT
Part of the git(1) suite
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