git-blame

GIT-BLAME(1)                       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 <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>


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.

       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


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>, -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.

       -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.

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 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

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.
       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

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
           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 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.

       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.

SEE ALSO
       git-annotate(1)

GIT
       Part of the git(1) suite



Git 2.30.0                         12/28/2020                       GIT-BLAME(1)