git-blame
(1)
Name
git-blame - Show what revision and author last modified each
line of a file
Synopsis
git blame [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-e] [-p] [-w] [--incremental] [-L n,m]
[-S <revs-file>] [-M] [-C] [-C] [-C] [--since=<date>] [--abbrev=<n>]
[<rev> | --contents <file> | --reverse <rev>] [--] <file>
Description
Git Manual GIT-BLAME(1)
NAME
git-blame - Show what revision and author last modified each
line of a file
SYNOPSIS
git blame [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-e] [-p] [-w] [--incremental] [-L n,m]
[-S <revs-file>] [-M] [-C] [-C] [-C] [--since=<date>] [--abbrev=<n>]
[<rev> | --contents <file> | --reverse <rev>] [--] <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.
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:
$ 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:
o number
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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.
--line-porcelain
Show the porcelain format, but output commit information
for each line, not just the first time a commit is
referenced. Implies --porcelain.
--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 the git-log(1) manual page.
--contents <file>
When <rev> is not specified, the command annotates the
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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:
{relative,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 traditional 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.
-h
Show help message.
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-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
filename 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.
-e, --show-email
Show the author email instead of author name (Default:
off).
-w
Ignore whitespace when comparing the parent's version
and the child's to find where the lines came from.
--abbrev=<n>
Instead of using the default 7+1 hexadecimal digits as
the abbreviated object name, use <n>+1 digits. Note that
1 column is used for a caret to mark the boundary
commit.
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.
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This header line is followed by the following information at
least once for each commit:
o the author name ("author"), email ("author-mail"), time
("author-time"), and timezone ("author-tz"); similarly
for committer.
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, prefixed by a TAB. This is to allow adding more
header elements later.
The porcelain format generally suppresses commit information
that has already been seen. For example, two lines that are
blamed to the same commit will both be shown, but the
details for that commit will be shown only once. This is
more efficient, but may require more state be kept by the
reader. The --line-porcelain option can be used to output
full commit information for each line, allowing simpler (but
less efficient) usage like:
# count the number of lines attributed to each author
git blame --line-porcelain file |
sed -n 's/^author //p' |
sort | uniq -c | sort -rn
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 similar to git rev-list:
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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
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 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
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for most scripting 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
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 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 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:
Joe Developer <joe@example.com>
Joe R. Developer <joe@example.com>
Jane Doe <jane@example.com>
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Jane Doe <jane@laptop.(none)>
Jane D. <jane@desktop.(none)>
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:
Jane Doe <jane@desktop.(none)>
Joe R. Developer <joe@example.com>
Note how there is no need for an entry for
<jane@laptop[1].(none)>, because the real name of that
author is already correct.
Example 2: Your repository contains commits from the
following authors:
nick1 <bugs@company.xx>
nick2 <bugs@company.xx>
nick2 <nick2@company.xx>
santa <me@company.xx>
claus <me@company.xx>
CTO <cto@coompany.xx>
Then you might want a .mailmap file that looks like:
<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>
Use hash # for comments that are either on their own line,
or after the email address.
ATTRIBUTES
See attributes(5) for descriptions of the following
attributes:
+---------------+--------------------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+--------------------------+
|Availability | developer/versioning/git |
+---------------+--------------------------+
|Stability | Uncommitted |
+---------------+--------------------------+
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SEE ALSO
git-annotate(1)
GIT
Part of the git(1) suite
NOTES
1. jane@laptop
mailto:jane@laptop
This software was built from source available at
https://java.net/projects/solaris-userland. The original
community source was downloaded from http://git-
core.googlecode.com/files/git-1.7.9.2.tar.gz
Further information about this software can be found on the
open source community website at http://git-scm.com/.
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