Documentation/git-blame.txt

   1 git-blame(1)
   2 ============
   3
   4 NAME
   5 ----
   6 git-blame - Show what revision and author last modified each line of a file
   7
   8 SYNOPSIS
   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>] [--] <file>
  14
  15 DESCRIPTION
  16 -----------
  17
  18 Annotates each line in the given file with information from the revision which
  19 last modified the line. Optionally, start annotating from the given revision.
  20
  21 Also it can limit the range of lines annotated.
  22
  23 This report doesn't tell you anything about lines which have been deleted or
  24 replaced; you need to use a tool such as linkgit:git-diff[1] or the "pickaxe"
  25 interface briefly mentioned in the following paragraph.
  26
  27 Apart from supporting file annotation, git also supports searching the
  28 development history for when a code snippet occurred in a change. This makes it
  29 possible to track when a code snippet was added to a file, moved or copied
  30 between files, and eventually deleted or replaced. It works by searching for
  31 a text string in the diff. A small example:
  32
  33 -----------------------------------------------------------------------------
  34 $ git log --pretty=oneline -S'blame_usage'
  35 5040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file>
  36 ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output
  37 -----------------------------------------------------------------------------
  38
  39 OPTIONS
  40 -------
  41 include::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         to be 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 filename in the original commit.  By default
  58         filename is shown if there is any line that came from a
  59         file with different name, due to rename detection.
  60
  61 -n::
  62 --show-number::
  63         Show line number in the original commit (Default: off).
  64
  65 -s::
  66         Suppress author name and timestamp from the output.
  67
  68 -w::
  69         Ignore whitespace when comparing parent's version and
  70         child's to find where the lines came from.
  71
  72
  73 THE PORCELAIN FORMAT
  74 --------------------
  75
  76 In this format, each line is output after a header; the
  77 header 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 line 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
  86 This header line is followed by the following information
  87 at least once for each commit:
  88
  89 - author name ("author"), email ("author-mail"), time
  90   ("author-time"), and timezone ("author-tz"); similarly
  91   for committer.
  92 - filename in the commit the line is attributed to.
  93 - the first line of the commit log message ("summary").
  94
  95 The contents of the actual line is output after the above
  96 header, prefixed by a TAB. This is to allow adding more
  97 header elements later.
  98
  99
 100 SPECIFYING RANGES
 101 -----------------
 102
 103 Unlike `git-blame` and `git-annotate` in older git, the extent
 104 of annotation can be limited to both line ranges and revision
 105 ranges.  When you are interested in finding the origin for
 106 ll. 40-60 for file `foo`, you can use `-L` option like these
 107 (they mean the same thing -- both ask for 21 lines starting at
 108 line 40):
 109
 110         git blame -L 40,60 foo
 111         git blame -L 40,+21 foo
 112
 113 Also you can use regular expression to specify the line range.
 114
 115         git blame -L '/^sub hello {/,/^}$/' foo
 116
 117 would limit the annotation to the body of `hello` subroutine.
 118
 119 When you are not interested in changes older than the version
 120 v2.6.18, or changes older than 3 weeks, you can use revision
 121 range specifiers  similar to `git-rev-list`:
 122
 123         git blame v2.6.18.. -- foo
 124         git blame --since=3.weeks -- foo
 125
 126 When revision range specifiers are used to limit the annotation,
 127 lines that have not changed since the range boundary (either the
 128 commit v2.6.18 or the most recent commit that is more than 3
 129 weeks old in the above example) are blamed for that range
 130 boundary commit.
 131
 132 A particularly useful way is to see if an added file have lines
 133 created by copy-and-paste from existing files.  Sometimes this
 134 indicates that the developer was being sloppy and did not
 135 refactor the code properly.  You can first find the commit that
 136 introduced the file with:
 137
 138         git log --diff-filter=A --pretty=short -- foo
 139
 140 and then annotate the change between the commit and its
 141 parents, using `commit{caret}!` notation:
 142
 143         git blame -C -C -f $commit^! -- foo
 144
 145
 146 INCREMENTAL OUTPUT
 147 ------------------
 148
 149 When called with `--incremental` option, the command outputs the
 150 result as it is built.  The output generally will talk about
 151 lines touched by more recent commits first (i.e. the lines will
 152 be annotated out of order) and is meant to be used by
 153 interactive viewers.
 154
 155 The output format is similar to the Porcelain format, but it
 156 does not contain the actual lines from the file that is being
 157 annotated.
 158
 159 . Each blame entry always starts with a line of:
 160
 161         <40-byte hex sha1> <sourceline> <resultline> <num_lines>
 162 +
 163 Line numbers count from 1.
 164
 165 . The first time that 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 about that "extended commit info" (author,
 168   email, committer, dates, summary etc).
 169
 170 . Unlike Porcelain format, the filename information is always
 171   given and terminates the entry:
 172
 173         "filename" <whitespace-quoted-filename-goes-here>
 174 +
 175 and thus it's really quite easy to parse for some line- and word-oriented
 176 parser (which should be quite natural for most scripting languages).
 177 +
 178 [NOTE]
 179 For people who do parsing: to make it more robust, just ignore any
 180 lines in between the first and last one ("<sha1>" and "filename" lines)
 181 where you don't recognize the tag-words (or care about that particular
 182 one) at the beginning of the "extended information" lines. That way, if
 183 there is ever added information (like the commit encoding or extended
 184 commit commentary), a blame viewer won't ever care.
 185
 186
 187 SEE ALSO
 188 --------
 189 linkgit:git-annotate[1]
 190
 191 AUTHOR
 192 ------
 193 Written by Junio C Hamano <junkio@cox.net>
 194
 195 GIT
 196 ---
 197 Part of the linkgit:git[1] suite