Documentation / git-blame.txton commit Merge git://git.kernel.org/pub/scm/gitk/gitk (1d7d6ad)
   1git-blame(1)
   2============
   3
   4NAME
   5----
   6git-blame - Show what revision and author last modified each line of a file
   7
   8SYNOPSIS
   9--------
  10[verse]
  11'git blame' [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-p] [-w] [--incremental] [-L n,m]
  12            [-S <revs-file>] [-M] [-C] [-C] [--since=<date>]
  13            [<rev> | --contents <file> | --reverse <rev>] [--] <file>
  14
  15DESCRIPTION
  16-----------
  17
  18Annotates each line in the given file with information from the revision which
  19last modified the line. Optionally, start annotating from the given revision.
  20
  21The command can also limit the range of lines annotated.
  22
  23The report does not tell you anything about lines which have been deleted or
  24replaced; you need to use a tool such as 'git-diff' or the "pickaxe"
  25interface briefly mentioned in the following paragraph.
  26
  27Apart from supporting file annotation, git also supports searching the
  28development history for when a code snippet occurred in a change. This makes it
  29possible to track when a code snippet was added to a file, moved or copied
  30between files, and eventually deleted or replaced. It works by searching for
  31a text string in the diff. A small example:
  32
  33-----------------------------------------------------------------------------
  34$ git log --pretty=oneline -S'blame_usage'
  355040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file>
  36ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output
  37-----------------------------------------------------------------------------
  38
  39OPTIONS
  40-------
  41include::blame-options.txt[]
  42
  43-c::
  44        Use the same output mode as linkgit:git-annotate[1] (Default: off).
  45
  46--score-debug::
  47        Include debugging information related to the movement of
  48        lines between files (see `-C`) and lines moved within a
  49        file (see `-M`).  The first number listed is the score.
  50        This is the number of alphanumeric characters detected
  51        as having been moved between or within files.  This must be above
  52        a certain threshold for 'git-blame' to consider those lines
  53        of code to have been moved.
  54
  55-f::
  56--show-name::
  57        Show the filename in the original commit.  By default
  58        the filename is shown if there is any line that came from a
  59        file with a different name, due to rename detection.
  60
  61-n::
  62--show-number::
  63        Show the line number in the original commit (Default: off).
  64
  65-s::
  66        Suppress the author name and timestamp from the output.
  67
  68-w::
  69        Ignore whitespace when comparing the parent's version and
  70        the child's to find where the lines came from.
  71
  72
  73THE PORCELAIN FORMAT
  74--------------------
  75
  76In this format, each line is output after a header; the
  77header at the minimum has the first line which has:
  78
  79- 40-byte SHA-1 of the commit the line is attributed to;
  80- the line number of the line in the original file;
  81- the line number of the line in the final file;
  82- on a line that starts a group of lines from a different
  83  commit than the previous one, the number of lines in this
  84  group.  On subsequent lines this field is absent.
  85
  86This header line is followed by the following information
  87at least once for each commit:
  88
  89- the author name ("author"), email ("author-mail"), time
  90  ("author-time"), and timezone ("author-tz"); similarly
  91  for committer.
  92- the filename in the commit that the line is attributed to.
  93- the first line of the commit log message ("summary").
  94
  95The contents of the actual line is output after the above
  96header, prefixed by a TAB. This is to allow adding more
  97header elements later.
  98
  99
 100SPECIFYING RANGES
 101-----------------
 102
 103Unlike 'git-blame' and 'git-annotate' in older versions of git, the extent
 104of the annotation can be limited to both line ranges and revision
 105ranges.  When you are interested in finding the origin for
 106lines 40-60 for file `foo`, you can use the `-L` option like so
 107(they mean the same thing -- both ask for 21 lines starting at
 108line 40):
 109
 110        git blame -L 40,60 foo
 111        git blame -L 40,+21 foo
 112
 113Also you can use a regular expression to specify the line range:
 114
 115        git blame -L '/^sub hello {/,/^}$/' foo
 116
 117which limits the annotation to the body of the `hello` subroutine.
 118
 119When you are not interested in changes older than version
 120v2.6.18, or changes older than 3 weeks, you can use revision
 121range specifiers  similar to 'git-rev-list':
 122
 123        git blame v2.6.18.. -- foo
 124        git blame --since=3.weeks -- foo
 125
 126When revision range specifiers are used to limit the annotation,
 127lines that have not changed since the range boundary (either the
 128commit v2.6.18 or the most recent commit that is more than 3
 129weeks old in the above example) are blamed for that range
 130boundary commit.
 131
 132A particularly useful way is to see if an added file has lines
 133created by copy-and-paste from existing files.  Sometimes this
 134indicates that the developer was being sloppy and did not
 135refactor the code properly.  You can first find the commit that
 136introduced the file with:
 137
 138        git log --diff-filter=A --pretty=short -- foo
 139
 140and then annotate the change between the commit and its
 141parents, using `commit{caret}!` notation:
 142
 143        git blame -C -C -f $commit^! -- foo
 144
 145
 146INCREMENTAL OUTPUT
 147------------------
 148
 149When called with `--incremental` option, the command outputs the
 150result as it is built.  The output generally will talk about
 151lines touched by more recent commits first (i.e. the lines will
 152be annotated out of order) and is meant to be used by
 153interactive viewers.
 154
 155The output format is similar to the Porcelain format, but it
 156does not contain the actual lines from the file that is being
 157annotated.
 158
 159. Each blame entry always starts with a line of:
 160
 161        <40-byte hex sha1> <sourceline> <resultline> <num_lines>
 162+
 163Line numbers count from 1.
 164
 165. The first time that a commit shows up in the stream, it has various
 166  other information about it printed out with a one-word tag at the
 167  beginning of each line describing the extra commit information (author,
 168  email, committer, dates, summary, etc.).
 169
 170. Unlike the Porcelain format, the filename information is always
 171  given and terminates the entry:
 172
 173        "filename" <whitespace-quoted-filename-goes-here>
 174+
 175and thus it is really quite easy to parse for some line- and word-oriented
 176parser (which should be quite natural for most scripting languages).
 177+
 178[NOTE]
 179For people who do parsing: to make it more robust, just ignore any
 180lines between the first and last one ("<sha1>" and "filename" lines)
 181where you do not recognize the tag words (or care about that particular
 182one) at the beginning of the "extended information" lines. That way, if
 183there is ever added information (like the commit encoding or extended
 184commit commentary), a blame viewer will not care.
 185
 186
 187MAPPING AUTHORS
 188---------------
 189
 190include::mailmap.txt[]
 191
 192
 193SEE ALSO
 194--------
 195linkgit:git-annotate[1]
 196
 197AUTHOR
 198------
 199Written by Junio C Hamano <gitster@pobox.com>
 200
 201GIT
 202---
 203Part of the linkgit:git[1] suite