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223 lines
7.3 KiB
223 lines
7.3 KiB
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> | --contents <file>] [--] <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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--contents <file>:: |
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When <rev> is not specified, the command annotates the |
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changes starting backwards from the working tree copy. |
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This flag makes the command pretend as if the working |
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tree copy has the contents of he named file (specify |
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`-` to make the command read from the standard input). |
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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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