235 lines
7.9 KiB
Plaintext
235 lines
7.9 KiB
Plaintext
git-blame(1)
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============
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NAME
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----
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git-blame - Show what revision and author last modified each line of a file
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SYNOPSIS
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--------
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[verse]
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'git blame' [-c] [-b] [-l] [--root] [-t] [-f] [-n] [-s] [-e] [-p] [-w] [--incremental]
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[-L <range>] [-S <revs-file>] [-M] [-C] [-C] [-C] [--since=<date>]
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[--abbrev=<n>] [<rev> | --contents <file> | --reverse <rev>] [--] <file>
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DESCRIPTION
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-----------
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Annotates each line in the given file with information from the revision which
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last modified the line. Optionally, start annotating from the given revision.
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When specified one or more times, `-L` restricts annotation to the requested
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lines.
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The origin of lines is automatically followed across whole-file
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renames (currently there is no option to turn the rename-following
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off). To follow lines moved from one file to another, or to follow
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lines that were copied and pasted from another file, etc., see the
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`-C` and `-M` options.
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The report does not tell you anything about lines which have been deleted or
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replaced; you need to use a tool such as 'git diff' or the "pickaxe"
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interface briefly mentioned in the following paragraph.
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Apart from supporting file annotation, Git also supports searching the
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development history for when a code snippet occurred in a change. This makes it
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possible to track when a code snippet was added to a file, moved or copied
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between files, and eventually deleted or replaced. It works by searching for
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a text string in the diff. A small example of the pickaxe interface
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that searches for `blame_usage`:
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-----------------------------------------------------------------------------
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$ git log --pretty=oneline -S'blame_usage'
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5040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file>
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ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output
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-----------------------------------------------------------------------------
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OPTIONS
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-------
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include::blame-options.txt[]
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-c::
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Use the same output mode as linkgit:git-annotate[1] (Default: off).
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--score-debug::
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Include debugging information related to the movement of
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lines between files (see `-C`) and lines moved within a
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file (see `-M`). The first number listed is the score.
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This is the number of alphanumeric characters detected
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as having been moved between or within files. This must be above
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a certain threshold for 'git blame' to consider those lines
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of code to have been moved.
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-f::
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--show-name::
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Show the filename in the original commit. By default
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the filename is shown if there is any line that came from a
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file with a different name, due to rename detection.
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-n::
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--show-number::
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Show the line number in the original commit (Default: off).
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-s::
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Suppress the author name and timestamp from the output.
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-e::
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--show-email::
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Show the author email instead of author name (Default: off).
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This can also be controlled via the `blame.showEmail` config
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option.
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-w::
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Ignore whitespace when comparing the parent's version and
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the child's to find where the lines came from.
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--abbrev=<n>::
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Instead of using the default 7+1 hexadecimal digits as the
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abbreviated object name, use <n>+1 digits. Note that 1 column
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is used for a caret to mark the boundary commit.
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THE PORCELAIN FORMAT
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--------------------
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In this format, each line is output after a header; the
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header at the minimum has the first line which has:
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- 40-byte SHA-1 of the commit the line is attributed to;
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- the line number of the line in the original file;
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- the line number of the line in the final file;
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- on a line that starts a group of lines from a different
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commit than the previous one, the number of lines in this
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group. On subsequent lines this field is absent.
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This header line is followed by the following information
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at least once for each commit:
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- the author name ("author"), email ("author-mail"), time
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("author-time"), and time zone ("author-tz"); similarly
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for committer.
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- the filename in the commit that the line is attributed to.
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- the first line of the commit log message ("summary").
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The contents of the actual line is output after the above
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header, prefixed by a TAB. This is to allow adding more
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header elements later.
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The porcelain format generally suppresses commit information that has
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already been seen. For example, two lines that are blamed to the same
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commit will both be shown, but the details for that commit will be shown
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only once. This is more efficient, but may require more state be kept by
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the reader. The `--line-porcelain` option can be used to output full
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commit information for each line, allowing simpler (but less efficient)
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usage like:
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# count the number of lines attributed to each author
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git blame --line-porcelain file |
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sed -n 's/^author //p' |
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sort | uniq -c | sort -rn
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SPECIFYING RANGES
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-----------------
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Unlike 'git blame' and 'git annotate' in older versions of git, the extent
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of the annotation can be limited to both line ranges and revision
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ranges. The `-L` option, which limits annotation to a range of lines, may be
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specified multiple times.
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When you are interested in finding the origin for
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lines 40-60 for file `foo`, you can use the `-L` option like so
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(they mean the same thing -- both ask for 21 lines starting at
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line 40):
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git blame -L 40,60 foo
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git blame -L 40,+21 foo
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Also you can use a regular expression to specify the line range:
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git blame -L '/^sub hello {/,/^}$/' foo
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which limits the annotation to the body of the `hello` subroutine.
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When you are not interested in changes older than version
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v2.6.18, or changes older than 3 weeks, you can use revision
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range specifiers similar to 'git rev-list':
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git blame v2.6.18.. -- foo
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git blame --since=3.weeks -- foo
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When revision range specifiers are used to limit the annotation,
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lines that have not changed since the range boundary (either the
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commit v2.6.18 or the most recent commit that is more than 3
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weeks old in the above example) are blamed for that range
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boundary commit.
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A particularly useful way is to see if an added file has lines
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created by copy-and-paste from existing files. Sometimes this
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indicates that the developer was being sloppy and did not
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refactor the code properly. You can first find the commit that
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introduced the file with:
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git log --diff-filter=A --pretty=short -- foo
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and then annotate the change between the commit and its
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parents, using `commit^!` notation:
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git blame -C -C -f $commit^! -- foo
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INCREMENTAL OUTPUT
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------------------
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When called with `--incremental` option, the command outputs the
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result as it is built. The output generally will talk about
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lines touched by more recent commits first (i.e. the lines will
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be annotated out of order) and is meant to be used by
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interactive viewers.
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The output format is similar to the Porcelain format, but it
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does not contain the actual lines from the file that is being
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annotated.
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. Each blame entry always starts with a line of:
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<40-byte hex sha1> <sourceline> <resultline> <num_lines>
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+
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Line numbers count from 1.
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. The first time that a commit shows up in the stream, it has various
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other information about it printed out with a one-word tag at the
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beginning of each line describing the extra commit information (author,
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email, committer, dates, summary, etc.).
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. Unlike the Porcelain format, the filename information is always
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given and terminates the entry:
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"filename" <whitespace-quoted-filename-goes-here>
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+
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and thus it is really quite easy to parse for some line- and word-oriented
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parser (which should be quite natural for most scripting languages).
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+
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[NOTE]
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For people who do parsing: to make it more robust, just ignore any
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lines between the first and last one ("<sha1>" and "filename" lines)
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where you do not recognize the tag words (or care about that particular
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one) at the beginning of the "extended information" lines. That way, if
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there is ever added information (like the commit encoding or extended
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commit commentary), a blame viewer will not care.
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MAPPING AUTHORS
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---------------
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include::mailmap.txt[]
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SEE ALSO
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--------
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linkgit:git-annotate[1]
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GIT
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---
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Part of the linkgit:git[1] suite
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