git-blame - Show what revision and author last modified each line
of a file
git blame [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-e] [-p] [-w] [--incremental]
[-L <range>] [-S <revs-file>] [-M] [-C] [-C] [-C] [--since=<date>]
[--ignore-rev <rev>] [--ignore-revs-file <file>]
[--color-lines] [--color-by-age] [--progress] [--abbrev=<n>]
[<rev> | --contents <file> | --reverse <rev>..<rev>] [--] <file>
Annotates each line in the given file with information from the
revision which last modified the line. Optionally, start annotating from the
given revision.
When specified one or more times, -L restricts annotation
to the requested lines.
The origin of lines is automatically followed across whole-file
renames (currently there is no option to turn the rename-following off). To
follow lines moved from one file to another, or to follow lines that were
copied and pasted from another file, etc., see the -C and -M
options.
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 of the pickaxe
interface that searches for blame_usage:
$ git log --pretty=oneline -S'blame_usage'
5040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file>
ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output
-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>, -L :<funcname>
Annotate only the line range given by
<start>,<end>, or by the function name regex
<funcname>. May be specified multiple times. Overlapping ranges
are allowed.
<start> and <end> are optional. -L
<start> or -L <start>, spans from
<start> to end of file. -L ,<end> spans from start
of file to <end>.
<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 <start> is a regex, it will search from the end of the
previous -L range, if any, otherwise from the start of file. If
<start> is ^/regex/, it will search from the start of
file. 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>.
If :<funcname> is given in place of
<start> and <end>, it is a regular expression that
denotes the range from the first funcname line that matches
<funcname>, up to the next funcname line.
:<funcname> searches from the end of the previous -L
range, if any, otherwise from the start of file. ^:<funcname>
searches from the start of file. The function names are determined in the
same way as git diff works out patch hunk headers (see Defining a
custom hunk-header in gitattributes(5)).
-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 <rev>..<rev>
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. git blame --reverse START is
taken as git blame --reverse START..HEAD for convenience.
--first-parent
Follow only the first parent commit upon seeing a merge
commit. This option can be used to determine when a line was introduced to a
particular integration branch, rather than when it was introduced to the
history overall.
-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 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>
Specifies the format used to output dates. 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
supported values, see the discussion of the --date option at
git-log(1).
--[no-]progress
Progress status is reported on the standard error stream
by default when it is attached to a terminal. This flag enables progress
reporting even if not attached to a terminal. Can’t use
--progress together with --porcelain or
--incremental.
-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.
--ignore-rev <rev>
Ignore changes made by the revision when assigning blame,
as if the change never happened. Lines that were changed or added by an
ignored commit will be blamed on the previous commit that changed that line or
nearby lines. This option may be specified multiple times to ignore more than
one revision. If the blame.markIgnoredLines config option is set, then
lines that were changed by an ignored commit and attributed to another commit
will be marked with a ? in the blame output. If the
blame.markUnblamableLines config option is set, then those lines
touched by an ignored commit that we could not attribute to another revision
are marked with a *.
--ignore-revs-file <file>
Ignore revisions listed in file, which must be in
the same format as an fsck.skipList. This option may be repeated, and
these files will be processed after any files specified with the
blame.ignoreRevsFile config option. An empty file name,
"", will clear the list of revs from previously processed
files.
--color-lines
Color line annotations in the default format differently
if they come from the same commit as the preceding line. This makes it easier
to distinguish code blocks introduced by different commits. The color defaults
to cyan and can be adjusted using the color.blame.repeatedLines config
option.
--color-by-age
Color line annotations depending on the age of the line
in the default format. The color.blame.highlightRecent config option
controls what color is used for each range of age.
-h
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
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). This can also be controlled via the blame.showEmail config
option.
-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 <m>+1 digits, where <m> is at
least <n> but ensures the commit object names are unique. Note that 1
column is used for a caret to mark the boundary commit.
When neither --porcelain nor --incremental option is
specified, git blame will output annotation for each line with:
•abbreviated object name for the commit the line
came from;
•author ident (by default author name and date,
unless -s or -e is specified); and
•line number
before the line contents.
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 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:
•the author name ("author"), email
("author-mail"), time ("author-time"), and time zone
("author-tz"); similarly for committer.
•the filename in the commit that 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.
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
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. The -L option, which limits annotation to a range of
lines, may be specified multiple times.
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:
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
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 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.
Everything below this line in this section is selectively included
from the git-config(1) documentation. The content is the same as
what’s found there:
blame.blankBoundary
Show blank commit object name for boundary commits in
git-blame(1). This option defaults to false.
blame.coloring
This determines the coloring scheme to be applied to
blame output. It can be repeatedLines, highlightRecent, or
none which is the default.
blame.date
Specifies the format used to output dates in
git-blame(1). If unset the iso format is used. For supported values,
see the discussion of the --date option at git-log(1).
blame.showEmail
Show the author email instead of author name in
git-blame(1). This option defaults to false.
blame.showRoot
Do not treat root commits as boundaries in
git-blame(1). This option defaults to false.
blame.ignoreRevsFile
Ignore revisions listed in the file, one unabbreviated
object name per line, in git-blame(1). Whitespace and comments
beginning with # are ignored. This option may be repeated multiple
times. Empty file names will reset the list of ignored revisions. This option
will be handled before the command line option
--ignore-revs-file.
blame.markUnblamableLines
Mark lines that were changed by an ignored revision that
we could not attribute to another commit with a * in the output of
git-blame(1).
blame.markIgnoredLines
Mark lines that were changed by an ignored revision that
we attributed to another commit with a ? in the output of
git-blame(1).