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https://github.com/git/git.git
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217 lines
7.0 KiB
Plaintext
217 lines
7.0 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] [-l] [-t] [-f] [-n] [-p] [--incremental] [-L n,m] [-S <revs-file>]
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[-M] [-C] [-C] [--since=<date>] [<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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Also it can limit the range of lines annotated.
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This report doesn't tell you anything about lines which have been deleted or
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replaced; you need to use a tool such as gitlink:git-diff[1] 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:
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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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-c, --compatibility::
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Use the same output mode as gitlink:git-annotate[1] (Default: off).
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-L n,m::
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Annotate only the specified line range (lines count from 1).
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-l, --long::
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Show long rev (Default: off).
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-t, --time::
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Show raw timestamp (Default: off).
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-S, --rev-file <revs-file>::
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Use revs from revs-file instead of calling gitlink:git-rev-list[1].
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-f, --show-name::
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Show filename in the original commit. By default
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filename is shown if there is any line that came from a
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file with different name, due to rename detection.
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-n, --show-number::
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Show line number in the original commit (Default: off).
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-p, --porcelain::
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Show in a format designed for machine consumption.
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--incremental::
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Show the result incrementally in a format designed for
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machine consumption.
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-M::
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Detect moving lines in the file as well. When a commit
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moves a block of lines in a file (e.g. the original file
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has A and then B, and the commit changes it to B and
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then A), traditional 'blame' algorithm typically blames
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the lines that were moved up (i.e. B) to the parent and
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assigns blame to the lines that were moved down (i.e. A)
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to the child commit. With this option, both groups of
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lines are blamed on the parent.
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-C::
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In addition to `-M`, detect lines copied from other
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files that were modified in the same commit. This is
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useful when you reorganize your program and move code
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around across files. When this option is given twice,
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the command looks for copies from all other files in the
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parent for the commit that creates the file in addition.
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-h, --help::
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Show help message.
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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 line 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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- author name ("author"), email ("author-mail"), time
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("author-time"), and timezone ("author-tz"); similarly
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for committer.
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- filename in the commit 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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SPECIFYING RANGES
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-----------------
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Unlike `git-blame` and `git-annotate` in older git, the extent
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of annotation can be limited to both line ranges and revision
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ranges. When you are interested in finding the origin for
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ll. 40-60 for file `foo`, you can use `-L` option like these
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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 regular expression to specify the line range.
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git blame -L '/^sub hello {/,/^}$/' foo
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would limit the annotation to the body of `hello` subroutine.
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When you are not interested in changes older than the 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 have 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{caret}!` 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 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 about that "extended commit info" (author,
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email, committer, dates, summary etc).
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. Unlike 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's 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 in between the first and last one ("<sha1>" and "filename" lines)
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where you don't 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 won't ever care.
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SEE ALSO
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--------
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gitlink:git-annotate[1]
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AUTHOR
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------
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Written by Junio C Hamano <junkio@cox.net>
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GIT
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---
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Part of the gitlink:git[7] suite
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