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diff --git a/Documentation/git-blame.txt b/Documentation/git-blame.txt new file mode 100644 index 0000000000..5c9888d014 --- /dev/null +++ b/Documentation/git-blame.txt @@ -0,0 +1,223 @@ +git-blame(1) +============ + +NAME +---- +git-blame - Show what revision and author last modified each line of a file + +SYNOPSIS +-------- +[verse] +'git-blame' [-c] [-l] [-t] [-f] [-n] [-p] [--incremental] [-L n,m] [-S <revs-file>] + [-M] [-C] [-C] [--since=<date>] [<rev> | --contents <file>] [--] <file> + +DESCRIPTION +----------- + +Annotates each line in the given file with information from the revision which +last modified the line. Optionally, start annotating from the given revision. + +Also it can limit the range of lines annotated. + +This report doesn't tell you anything about lines which have been deleted or +replaced; you need to use a tool such as gitlink:git-diff[1] or the "pickaxe" +interface briefly mentioned in the following paragraph. + +Apart from supporting file annotation, git also supports searching the +development history for when a code snippet occurred in a change. This makes it +possible to track when a code snippet was added to a file, moved or copied +between files, and eventually deleted or replaced. It works by searching for +a text string in the diff. A small example: + +----------------------------------------------------------------------------- +$ git log --pretty=oneline -S'blame_usage' +5040f17eba15504bad66b14a645bddd9b015ebb7 blame -S <ancestry-file> +ea4c7f9bf69e781dd0cd88d2bccb2bf5cc15c9a7 git-blame: Make the output +----------------------------------------------------------------------------- + +OPTIONS +------- +-c, --compatibility:: + Use the same output mode as gitlink:git-annotate[1] (Default: off). + +-L n,m:: + Annotate only the specified line range (lines count from 1). + +-l, --long:: + Show long rev (Default: off). + +-t, --time:: + Show raw timestamp (Default: off). + +-S, --rev-file <revs-file>:: + Use revs from revs-file instead of calling gitlink:git-rev-list[1]. + +-f, --show-name:: + Show filename in the original commit. By default + filename is shown if there is any line that came from a + file with different name, due to rename detection. + +-n, --show-number:: + Show line number in the original commit (Default: off). + +-p, --porcelain:: + Show in a format designed for machine consumption. + +--incremental:: + Show the result incrementally in a format designed for + machine consumption. + +--contents <file>:: + When <rev> is not specified, the command annotates the + changes starting backwards from the working tree copy. + This flag makes the command pretend as if the working + tree copy has the contents of he named file (specify + `-` to make the command read from the standard input). + +-M:: + Detect moving lines in the file as well. When a commit + moves a block of lines in a file (e.g. the original file + has A and then B, and the commit changes it to B and + then A), traditional 'blame' algorithm typically blames + the lines that were moved up (i.e. B) to the parent and + assigns blame to the lines that were moved down (i.e. A) + to the child commit. With this option, both groups of + lines are blamed on the parent. + +-C:: + In addition to `-M`, detect lines copied from other + files that were modified in the same commit. This is + useful when you reorganize your program and move code + around across files. When this option is given twice, + the command looks for copies from all other files in the + parent for the commit that creates the file in addition. + +-h, --help:: + Show help message. + + +THE PORCELAIN FORMAT +-------------------- + +In this format, each line is output after a header; the +header at the minimum has the first line which has: + +- 40-byte SHA-1 of the commit the line is attributed to; +- the line number of the line in the original file; +- the line number of the line in the final file; +- on a line that starts a group of line from a different + commit than the previous one, the number of lines in this + group. On subsequent lines this field is absent. + +This header line is followed by the following information +at least once for each commit: + +- author name ("author"), email ("author-mail"), time + ("author-time"), and timezone ("author-tz"); similarly + for committer. +- filename in the commit the line is attributed to. +- the first line of the commit log message ("summary"). + +The contents of the actual line is output after the above +header, prefixed by a TAB. This is to allow adding more +header elements later. + + +SPECIFYING RANGES +----------------- + +Unlike `git-blame` and `git-annotate` in older git, the extent +of annotation can be limited to both line ranges and revision +ranges. When you are interested in finding the origin for +ll. 40-60 for file `foo`, you can use `-L` option like these +(they mean the same thing -- both ask for 21 lines starting at +line 40): + + git blame -L 40,60 foo + git blame -L 40,+21 foo + +Also you can use regular expression to specify the line range. + + git blame -L '/^sub hello {/,/^}$/' foo + +would limit the annotation to the body of `hello` subroutine. + +When you are not interested in changes older than the version +v2.6.18, or changes older than 3 weeks, you can use revision +range specifiers similar to `git-rev-list`: + + git blame v2.6.18.. -- foo + git blame --since=3.weeks -- foo + +When revision range specifiers are used to limit the annotation, +lines that have not changed since the range boundary (either the +commit v2.6.18 or the most recent commit that is more than 3 +weeks old in the above example) are blamed for that range +boundary commit. + +A particularly useful way is to see if an added file have lines +created by copy-and-paste from existing files. Sometimes this +indicates that the developer was being sloppy and did not +refactor the code properly. You can first find the commit that +introduced the file with: + + git log --diff-filter=A --pretty=short -- foo + +and then annotate the change between the commit and its +parents, using `commit{caret}!` notation: + + git blame -C -C -f $commit^! -- foo + + +INCREMENTAL OUTPUT +------------------ + +When called with `--incremental` option, the command outputs the +result as it is built. The output generally will talk about +lines touched by more recent commits first (i.e. the lines will +be annotated out of order) and is meant to be used by +interactive viewers. + +The output format is similar to the Porcelain format, but it +does not contain the actual lines from the file that is being +annotated. + +. Each blame entry always starts with a line of: + + <40-byte hex sha1> <sourceline> <resultline> <num_lines> ++ +Line numbers count from 1. + +. The first time that commit shows up in the stream, it has various + other information about it printed out with a one-word tag at the + beginning of each line about that "extended commit info" (author, + email, committer, dates, summary etc). + +. Unlike Porcelain format, the filename information is always + given and terminates the entry: + + "filename" <whitespace-quoted-filename-goes-here> ++ +and thus it's really quite easy to parse for some line- and word-oriented +parser (which should be quite natural for most scripting languages). ++ +[NOTE] +For people who do parsing: to make it more robust, just ignore any +lines in between the first and last one ("<sha1>" and "filename" lines) +where you don't recognize the tag-words (or care about that particular +one) at the beginning of the "extended information" lines. That way, if +there is ever added information (like the commit encoding or extended +commit commentary), a blame viewer won't ever care. + + +SEE ALSO +-------- +gitlink:git-annotate[1] + +AUTHOR +------ +Written by Junio C Hamano <junkio@cox.net> + +GIT +--- +Part of the gitlink:git[7] suite |