Documentation / git-blame.txton commit Merge branch 'en/merge-options-ff-and-friends' (9bc67b6)
   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] [-e] [-p] [-w] [--incremental]
  12            [-L <range>] [-S <revs-file>] [-M] [-C] [-C] [-C] [--since=<date>]
  13            [--ignore-rev <rev>] [--ignore-revs-file <file>]
  14            [--progress] [--abbrev=<n>] [<rev> | --contents <file> | --reverse <rev>..<rev>]
  15            [--] <file>
  16
  17DESCRIPTION
  18-----------
  19
  20Annotates each line in the given file with information from the revision which
  21last modified the line. Optionally, start annotating from the given revision.
  22
  23When specified one or more times, `-L` restricts annotation to the requested
  24lines.
  25
  26The origin of lines is automatically followed across whole-file
  27renames (currently there is no option to turn the rename-following
  28off). To follow lines moved from one file to another, or to follow
  29lines that were copied and pasted from another file, etc., see the
  30`-C` and `-M` options.
  31
  32The report does not tell you anything about lines which have been deleted or
  33replaced; you need to use a tool such as 'git diff' or the "pickaxe"
  34interface briefly mentioned in the following paragraph.
  35
  36Apart from supporting file annotation, Git also supports searching the
  37development history for when a code snippet occurred in a change. This makes it
  38possible to track when a code snippet was added to a file, moved or copied
  39between files, and eventually deleted or replaced. It works by searching for
  40a text string in the diff. A small example of the pickaxe interface
  41that searches for `blame_usage`:
  42
  43-----------------------------------------------------------------------------
  44$ git log --pretty=oneline -S'blame_usage'
  455040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file>
  46ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output
  47-----------------------------------------------------------------------------
  48
  49OPTIONS
  50-------
  51include::blame-options.txt[]
  52
  53-c::
  54        Use the same output mode as linkgit:git-annotate[1] (Default: off).
  55
  56--score-debug::
  57        Include debugging information related to the movement of
  58        lines between files (see `-C`) and lines moved within a
  59        file (see `-M`).  The first number listed is the score.
  60        This is the number of alphanumeric characters detected
  61        as having been moved between or within files.  This must be above
  62        a certain threshold for 'git blame' to consider those lines
  63        of code to have been moved.
  64
  65-f::
  66--show-name::
  67        Show the filename in the original commit.  By default
  68        the filename is shown if there is any line that came from a
  69        file with a different name, due to rename detection.
  70
  71-n::
  72--show-number::
  73        Show the line number in the original commit (Default: off).
  74
  75-s::
  76        Suppress the author name and timestamp from the output.
  77
  78-e::
  79--show-email::
  80        Show the author email instead of author name (Default: off).
  81        This can also be controlled via the `blame.showEmail` config
  82        option.
  83
  84-w::
  85        Ignore whitespace when comparing the parent's version and
  86        the child's to find where the lines came from.
  87
  88--abbrev=<n>::
  89        Instead of using the default 7+1 hexadecimal digits as the
  90        abbreviated object name, use <n>+1 digits. Note that 1 column
  91        is used for a caret to mark the boundary commit.
  92
  93
  94THE PORCELAIN FORMAT
  95--------------------
  96
  97In this format, each line is output after a header; the
  98header at the minimum has the first line which has:
  99
 100- 40-byte SHA-1 of the commit the line is attributed to;
 101- the line number of the line in the original file;
 102- the line number of the line in the final file;
 103- on a line that starts a group of lines from a different
 104  commit than the previous one, the number of lines in this
 105  group.  On subsequent lines this field is absent.
 106
 107This header line is followed by the following information
 108at least once for each commit:
 109
 110- the author name ("author"), email ("author-mail"), time
 111  ("author-time"), and time zone ("author-tz"); similarly
 112  for committer.
 113- the filename in the commit that the line is attributed to.
 114- the first line of the commit log message ("summary").
 115
 116The contents of the actual line is output after the above
 117header, prefixed by a TAB. This is to allow adding more
 118header elements later.
 119
 120The porcelain format generally suppresses commit information that has
 121already been seen. For example, two lines that are blamed to the same
 122commit will both be shown, but the details for that commit will be shown
 123only once. This is more efficient, but may require more state be kept by
 124the reader. The `--line-porcelain` option can be used to output full
 125commit information for each line, allowing simpler (but less efficient)
 126usage like:
 127
 128        # count the number of lines attributed to each author
 129        git blame --line-porcelain file |
 130        sed -n 's/^author //p' |
 131        sort | uniq -c | sort -rn
 132
 133
 134SPECIFYING RANGES
 135-----------------
 136
 137Unlike 'git blame' and 'git annotate' in older versions of git, the extent
 138of the annotation can be limited to both line ranges and revision
 139ranges. The `-L` option, which limits annotation to a range of lines, may be
 140specified multiple times.
 141
 142When you are interested in finding the origin for
 143lines 40-60 for file `foo`, you can use the `-L` option like so
 144(they mean the same thing -- both ask for 21 lines starting at
 145line 40):
 146
 147        git blame -L 40,60 foo
 148        git blame -L 40,+21 foo
 149
 150Also you can use a regular expression to specify the line range:
 151
 152        git blame -L '/^sub hello {/,/^}$/' foo
 153
 154which limits the annotation to the body of the `hello` subroutine.
 155
 156When you are not interested in changes older than version
 157v2.6.18, or changes older than 3 weeks, you can use revision
 158range specifiers  similar to 'git rev-list':
 159
 160        git blame v2.6.18.. -- foo
 161        git blame --since=3.weeks -- foo
 162
 163When revision range specifiers are used to limit the annotation,
 164lines that have not changed since the range boundary (either the
 165commit v2.6.18 or the most recent commit that is more than 3
 166weeks old in the above example) are blamed for that range
 167boundary commit.
 168
 169A particularly useful way is to see if an added file has lines
 170created by copy-and-paste from existing files.  Sometimes this
 171indicates that the developer was being sloppy and did not
 172refactor the code properly.  You can first find the commit that
 173introduced the file with:
 174
 175        git log --diff-filter=A --pretty=short -- foo
 176
 177and then annotate the change between the commit and its
 178parents, using `commit^!` notation:
 179
 180        git blame -C -C -f $commit^! -- foo
 181
 182
 183INCREMENTAL OUTPUT
 184------------------
 185
 186When called with `--incremental` option, the command outputs the
 187result as it is built.  The output generally will talk about
 188lines touched by more recent commits first (i.e. the lines will
 189be annotated out of order) and is meant to be used by
 190interactive viewers.
 191
 192The output format is similar to the Porcelain format, but it
 193does not contain the actual lines from the file that is being
 194annotated.
 195
 196. Each blame entry always starts with a line of:
 197
 198        <40-byte hex sha1> <sourceline> <resultline> <num_lines>
 199+
 200Line numbers count from 1.
 201
 202. The first time that a commit shows up in the stream, it has various
 203  other information about it printed out with a one-word tag at the
 204  beginning of each line describing the extra commit information (author,
 205  email, committer, dates, summary, etc.).
 206
 207. Unlike the Porcelain format, the filename information is always
 208  given and terminates the entry:
 209
 210        "filename" <whitespace-quoted-filename-goes-here>
 211+
 212and thus it is really quite easy to parse for some line- and word-oriented
 213parser (which should be quite natural for most scripting languages).
 214+
 215[NOTE]
 216For people who do parsing: to make it more robust, just ignore any
 217lines between the first and last one ("<sha1>" and "filename" lines)
 218where you do not recognize the tag words (or care about that particular
 219one) at the beginning of the "extended information" lines. That way, if
 220there is ever added information (like the commit encoding or extended
 221commit commentary), a blame viewer will not care.
 222
 223
 224MAPPING AUTHORS
 225---------------
 226
 227include::mailmap.txt[]
 228
 229
 230SEE ALSO
 231--------
 232linkgit:git-annotate[1]
 233
 234GIT
 235---
 236Part of the linkgit:git[1] suite