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] [-e] [-p] [-w] [--incremental]
  12             [-L <range>] [-S <revs-file>] [-M] [-C] [-C] [-C] [--since=<date>]
  13             [--progress] [--abbrev=<n>] [<rev> | --contents <file> | --reverse <rev>..<rev>]
  14             [--] <file>
  15
  16 DESCRIPTION
  17 -----------
  18
  19 Annotates each line in the given file with information from the revision which
  20 last modified the line. Optionally, start annotating from the given revision.
  21
  22 When specified one or more times, `-L` restricts annotation to the requested
  23 lines.
  24
  25 The origin of lines is automatically followed across whole-file
  26 renames (currently there is no option to turn the rename-following
  27 off). To follow lines moved from one file to another, or to follow
  28 lines that were copied and pasted from another file, etc., see the
  29 `-C` and `-M` options.
  30
  31 The report does not tell you anything about lines which have been deleted or
  32 replaced; you need to use a tool such as 'git diff' or the "pickaxe"
  33 interface briefly mentioned in the following paragraph.
  34
  35 Apart from supporting file annotation, Git also supports searching the
  36 development history for when a code snippet occurred in a change. This makes it
  37 possible to track when a code snippet was added to a file, moved or copied
  38 between files, and eventually deleted or replaced. It works by searching for
  39 a text string in the diff. A small example of the pickaxe interface
  40 that searches for `blame_usage`:
  41
  42 -----------------------------------------------------------------------------
  43 $ git log --pretty=oneline -S'blame_usage'
  44 5040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file>
  45 ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output
  46 -----------------------------------------------------------------------------
  47
  48 OPTIONS
  49 -------
  50 include::blame-options.txt[]
  51
  52 -c::
  53         Use the same output mode as linkgit:git-annotate[1] (Default: off).
  54
  55 --score-debug::
  56         Include debugging information related to the movement of
  57         lines between files (see `-C`) and lines moved within a
  58         file (see `-M`).  The first number listed is the score.
  59         This is the number of alphanumeric characters detected
  60         as having been moved between or within files.  This must be above
  61         a certain threshold for 'git blame' to consider those lines
  62         of code to have been moved.
  63
  64 -f::
  65 --show-name::
  66         Show the filename in the original commit.  By default
  67         the filename is shown if there is any line that came from a
  68         file with a different name, due to rename detection.
  69
  70 -n::
  71 --show-number::
  72         Show the line number in the original commit (Default: off).
  73
  74 -s::
  75         Suppress the author name and timestamp from the output.
  76
  77 -e::
  78 --show-email::
  79         Show the author email instead of author name (Default: off).
  80         This can also be controlled via the `blame.showEmail` config
  81         option.
  82
  83 -w::
  84         Ignore whitespace when comparing the parent's version and
  85         the child's to find where the lines came from.
  86
  87 --abbrev=<n>::
  88         Instead of using the default 7+1 hexadecimal digits as the
  89         abbreviated object name, use <n>+1 digits. Note that 1 column
  90         is used for a caret to mark the boundary commit.
  91
  92
  93 THE PORCELAIN FORMAT
  94 --------------------
  95
  96 In this format, each line is output after a header; the
  97 header at the minimum has the first line which has:
  98
  99 - 40-byte SHA-1 of the commit the line is attributed to;
 100 - the line number of the line in the original file;
 101 - the line number of the line in the final file;
 102 - on a line that starts a group of lines from a different
 103   commit than the previous one, the number of lines in this
 104   group.  On subsequent lines this field is absent.
 105
 106 This header line is followed by the following information
 107 at least once for each commit:
 108
 109 - the author name ("author"), email ("author-mail"), time
 110   ("author-time"), and time zone ("author-tz"); similarly
 111   for committer.
 112 - the filename in the commit that the line is attributed to.
 113 - the first line of the commit log message ("summary").
 114
 115 The contents of the actual line is output after the above
 116 header, prefixed by a TAB. This is to allow adding more
 117 header elements later.
 118
 119 The porcelain format generally suppresses commit information that has
 120 already been seen. For example, two lines that are blamed to the same
 121 commit will both be shown, but the details for that commit will be shown
 122 only once. This is more efficient, but may require more state be kept by
 123 the reader. The `--line-porcelain` option can be used to output full
 124 commit information for each line, allowing simpler (but less efficient)
 125 usage like:
 126
 127         # count the number of lines attributed to each author
 128         git blame --line-porcelain file |
 129         sed -n 's/^author //p' |
 130         sort | uniq -c | sort -rn
 131
 132
 133 SPECIFYING RANGES
 134 -----------------
 135
 136 Unlike 'git blame' and 'git annotate' in older versions of git, the extent
 137 of the annotation can be limited to both line ranges and revision
 138 ranges. The `-L` option, which limits annotation to a range of lines, may be
 139 specified multiple times.
 140
 141 When you are interested in finding the origin for
 142 lines 40-60 for file `foo`, you can use the `-L` option like so
 143 (they mean the same thing -- both ask for 21 lines starting at
 144 line 40):
 145
 146         git blame -L 40,60 foo
 147         git blame -L 40,+21 foo
 148
 149 Also you can use a regular expression to specify the line range:
 150
 151         git blame -L '/^sub hello {/,/^}$/' foo
 152
 153 which limits the annotation to the body of the `hello` subroutine.
 154
 155 When you are not interested in changes older than version
 156 v2.6.18, or changes older than 3 weeks, you can use revision
 157 range specifiers  similar to 'git rev-list':
 158
 159         git blame v2.6.18.. -- foo
 160         git blame --since=3.weeks -- foo
 161
 162 When revision range specifiers are used to limit the annotation,
 163 lines that have not changed since the range boundary (either the
 164 commit v2.6.18 or the most recent commit that is more than 3
 165 weeks old in the above example) are blamed for that range
 166 boundary commit.
 167
 168 A particularly useful way is to see if an added file has lines
 169 created by copy-and-paste from existing files.  Sometimes this
 170 indicates that the developer was being sloppy and did not
 171 refactor the code properly.  You can first find the commit that
 172 introduced the file with:
 173
 174         git log --diff-filter=A --pretty=short -- foo
 175
 176 and then annotate the change between the commit and its
 177 parents, using `commit^!` notation:
 178
 179         git blame -C -C -f $commit^! -- foo
 180
 181
 182 INCREMENTAL OUTPUT
 183 ------------------
 184
 185 When called with `--incremental` option, the command outputs the
 186 result as it is built.  The output generally will talk about
 187 lines touched by more recent commits first (i.e. the lines will
 188 be annotated out of order) and is meant to be used by
 189 interactive viewers.
 190
 191 The output format is similar to the Porcelain format, but it
 192 does not contain the actual lines from the file that is being
 193 annotated.
 194
 195 . Each blame entry always starts with a line of:
 196
 197         <40-byte hex sha1> <sourceline> <resultline> <num_lines>
 198 +
 199 Line numbers count from 1.
 200
 201 . The first time that a commit shows up in the stream, it has various
 202   other information about it printed out with a one-word tag at the
 203   beginning of each line describing the extra commit information (author,
 204   email, committer, dates, summary, etc.).
 205
 206 . Unlike the Porcelain format, the filename information is always
 207   given and terminates the entry:
 208
 209         "filename" <whitespace-quoted-filename-goes-here>
 210 +
 211 and thus it is really quite easy to parse for some line- and word-oriented
 212 parser (which should be quite natural for most scripting languages).
 213 +
 214 [NOTE]
 215 For people who do parsing: to make it more robust, just ignore any
 216 lines between the first and last one ("<sha1>" and "filename" lines)
 217 where you do not recognize the tag words (or care about that particular
 218 one) at the beginning of the "extended information" lines. That way, if
 219 there is ever added information (like the commit encoding or extended
 220 commit commentary), a blame viewer will not care.
 221
 222
 223 MAPPING AUTHORS
 224 ---------------
 225
 226 include::mailmap.txt[]
 227
 228
 229 SEE ALSO
 230 --------
 231 linkgit:git-annotate[1]
 232
 233 GIT
 234 ---
 235 Part of the linkgit:git[1] suite