git-blame






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>]
            [−−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.









                             ‐2‐


     −−show−stats
     Include additional statistics at the end of blame
     output.

     −L <start>,<end>, −L :<funcname>
     Annotate only the given line range. 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.

     −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).











                             ‐3‐


     −−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.

     −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









                             ‐4‐


     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









                             ‐5‐


     revs from previously processed files.

     −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 <n>+1 digits. Note
     that 1 column is used for a caret to mark the boundary
     commit.



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;









                             ‐6‐


 •   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:









                             ‐7‐


     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.).









                             ‐8‐


  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.



If the file .mailmap exists at the toplevel of the
repository, or at the location pointed to by the
mailmap.file or mailmap.blob configuration options, 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.










                             ‐9‐


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>
     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.(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.



git‐annotate(1)



Part of the git(1) suite