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             [--ignore-rev <rev>] [--ignore-revs-file <file>]
  14             [--color-lines] [--color-by-age] [--progress] [--abbrev=<n>]
  15             [<rev> | --contents <file> | --reverse <rev>..<rev>] [--] <file>
  16
  17 DESCRIPTION
  18 -----------
  19
  20 Annotates each line in the given file with information from the revision which
  21 last modified the line. Optionally, start annotating from the given revision.
  22
  23 When specified one or more times, `-L` restricts annotation to the requested
  24 lines.
  25
  26 The origin of lines is automatically followed across whole-file
  27 renames (currently there is no option to turn the rename-following
  28 off). To follow lines moved from one file to another, or to follow
  29 lines that were copied and pasted from another file, etc., see the
  30 `-C` and `-M` options.
  31
  32 The report does not tell you anything about lines which have been deleted or
  33 replaced; you need to use a tool such as 'git diff' or the "pickaxe"
  34 interface briefly mentioned in the following paragraph.
  35
  36 Apart from supporting file annotation, Git also supports searching the
  37 development history for when a code snippet occurred in a change. This makes it
  38 possible to track when a code snippet was added to a file, moved or copied
  39 between files, and eventually deleted or replaced. It works by searching for
  40 a text string in the diff. A small example of the pickaxe interface
  41 that searches for `blame_usage`:
  42
  43 -----------------------------------------------------------------------------
  44 $ git log --pretty=oneline -S'blame_usage'
  45 5040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file>
  46 ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output
  47 -----------------------------------------------------------------------------
  48
  49 OPTIONS
  50 -------
  51 include::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 <m>+1 digits, where <m> is at
  91         least <n> but ensures the commit object names are unique.
  92         Note that 1 column
  93         is used for a caret to mark the boundary commit.
  94
  95
  96 THE DEFAULT FORMAT
  97 ------------------
  98
  99 When neither `--porcelain` nor `--incremental` option is specified,
 100 `git blame` will output annotation for each line with:
 101
 102 - abbreviated object name for the commit the line came from;
 103 - author ident (by default author name and date, unless `-s` or `-e`
 104   is specified); and
 105 - line number
 106
 107 before the line contents.
 108
 109 THE PORCELAIN FORMAT
 110 --------------------
 111
 112 In this format, each line is output after a header; the
 113 header at the minimum has the first line which has:
 114
 115 - 40-byte SHA-1 of the commit the line is attributed to;
 116 - the line number of the line in the original file;
 117 - the line number of the line in the final file;
 118 - on a line that starts a group of lines from a different
 119   commit than the previous one, the number of lines in this
 120   group.  On subsequent lines this field is absent.
 121
 122 This header line is followed by the following information
 123 at least once for each commit:
 124
 125 - the author name ("author"), email ("author-mail"), time
 126   ("author-time"), and time zone ("author-tz"); similarly
 127   for committer.
 128 - the filename in the commit that the line is attributed to.
 129 - the first line of the commit log message ("summary").
 130
 131 The contents of the actual line is output after the above
 132 header, prefixed by a TAB. This is to allow adding more
 133 header elements later.
 134
 135 The porcelain format generally suppresses commit information that has
 136 already been seen. For example, two lines that are blamed to the same
 137 commit will both be shown, but the details for that commit will be shown
 138 only once. This is more efficient, but may require more state be kept by
 139 the reader. The `--line-porcelain` option can be used to output full
 140 commit information for each line, allowing simpler (but less efficient)
 141 usage like:
 142
 143         # count the number of lines attributed to each author
 144         git blame --line-porcelain file |
 145         sed -n 's/^author //p' |
 146         sort | uniq -c | sort -rn
 147
 148
 149 SPECIFYING RANGES
 150 -----------------
 151
 152 Unlike 'git blame' and 'git annotate' in older versions of git, the extent
 153 of the annotation can be limited to both line ranges and revision
 154 ranges. The `-L` option, which limits annotation to a range of lines, may be
 155 specified multiple times.
 156
 157 When you are interested in finding the origin for
 158 lines 40-60 for file `foo`, you can use the `-L` option like so
 159 (they mean the same thing -- both ask for 21 lines starting at
 160 line 40):
 161
 162         git blame -L 40,60 foo
 163         git blame -L 40,+21 foo
 164
 165 Also you can use a regular expression to specify the line range:
 166
 167         git blame -L '/^sub hello {/,/^}$/' foo
 168
 169 which limits the annotation to the body of the `hello` subroutine.
 170
 171 When you are not interested in changes older than version
 172 v2.6.18, or changes older than 3 weeks, you can use revision
 173 range specifiers  similar to 'git rev-list':
 174
 175         git blame v2.6.18.. -- foo
 176         git blame --since=3.weeks -- foo
 177
 178 When revision range specifiers are used to limit the annotation,
 179 lines that have not changed since the range boundary (either the
 180 commit v2.6.18 or the most recent commit that is more than 3
 181 weeks old in the above example) are blamed for that range
 182 boundary commit.
 183
 184 A particularly useful way is to see if an added file has lines
 185 created by copy-and-paste from existing files.  Sometimes this
 186 indicates that the developer was being sloppy and did not
 187 refactor the code properly.  You can first find the commit that
 188 introduced the file with:
 189
 190         git log --diff-filter=A --pretty=short -- foo
 191
 192 and then annotate the change between the commit and its
 193 parents, using `commit^!` notation:
 194
 195         git blame -C -C -f $commit^! -- foo
 196
 197
 198 INCREMENTAL OUTPUT
 199 ------------------
 200
 201 When called with `--incremental` option, the command outputs the
 202 result as it is built.  The output generally will talk about
 203 lines touched by more recent commits first (i.e. the lines will
 204 be annotated out of order) and is meant to be used by
 205 interactive viewers.
 206
 207 The output format is similar to the Porcelain format, but it
 208 does not contain the actual lines from the file that is being
 209 annotated.
 210
 211 . Each blame entry always starts with a line of:
 212
 213         <40-byte hex sha1> <sourceline> <resultline> <num_lines>
 214 +
 215 Line numbers count from 1.
 216
 217 . The first time that a commit shows up in the stream, it has various
 218   other information about it printed out with a one-word tag at the
 219   beginning of each line describing the extra commit information (author,
 220   email, committer, dates, summary, etc.).
 221
 222 . Unlike the Porcelain format, the filename information is always
 223   given and terminates the entry:
 224
 225         "filename" <whitespace-quoted-filename-goes-here>
 226 +
 227 and thus it is really quite easy to parse for some line- and word-oriented
 228 parser (which should be quite natural for most scripting languages).
 229 +
 230 [NOTE]
 231 For people who do parsing: to make it more robust, just ignore any
 232 lines between the first and last one ("<sha1>" and "filename" lines)
 233 where you do not recognize the tag words (or care about that particular
 234 one) at the beginning of the "extended information" lines. That way, if
 235 there is ever added information (like the commit encoding or extended
 236 commit commentary), a blame viewer will not care.
 237
 238
 239 MAPPING AUTHORS
 240 ---------------
 241
 242 See linkgit:gitmailmap[5].
 243
 244 CONFIGURATION
 245 -------------
 246
 247 include::includes/cmd-config-section-all.txt[]
 248
 249 include::config/blame.txt[]
 250
 251 SEE ALSO
 252 --------
 253 linkgit:git-annotate[1]
 254
 255 GIT
 256 ---
 257 Part of the linkgit:git[1] suite