User Tools

Site Tools


git_blame

This is an old revision of the document!


Overview

Most useful variations of git blame, using examples from Linux kernel source.

From man git-annotate:

The only difference between this command and git-blame(1) is
that they use slightly different output formats, and this
command exists only for backward compatibility to support
existing scripts, and provide a more familiar command name for
people coming from other SCM systems.

Basic usage

Show the (most recent) origin of each line in a file:

$ git blame Makefile
b24413180f560 (Greg Kroah-Hartman       2017-11-01 15:07:57 +0100    1) # SPDX-License-Identifier: GPL-2.0
bfeffd1552837 (Linus Torvalds           2019-01-06 17:08:20 -0800    2) VERSION = 5
bfeffd1552837 (Linus Torvalds           2019-01-06 17:08:20 -0800    3) PATCHLEVEL = 0
55922c9d1b84b (Linus Torvalds           2011-05-29 17:43:36 -0700    4) SUBLEVEL = 0
d13937116f1e8 (Linus Torvalds           2019-02-10 14:42:20 -0800    5) EXTRAVERSION = -rc6
2e6e902d18502 (Linus Torvalds           2018-11-25 14:19:31 -0800    6) NAME = Shy Crocodile
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700    7) 
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700    8) # *DOCUMENTATION*
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700    9) # To see a list of typical targets execute "make help"
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700   10) # More info can be located in ./README
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700   11) # Comments in this file are targeted only to the developer, do not
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700   12) # expect to learn how to build the kernel reading this file.
^1da177e4c3f4 (Linus Torvalds           2005-04-16 15:20:36 -0700   13)
... snip ...

You can also use -L for line limiting:

$ git blame -L 1420,1430 Makefile
433db3e260bc8 (Vinícius Tinti   2017-04-24 13:04:58 -0700 1420)         @echo  '                    (requires compiler support for LLVM assembly generation)'
6271897978072 (Joe Perches      2010-01-13 09:31:44 -0800 1421)         @echo  '  dir/file.lst    - Build specified mixed source/assembly target only'
6271897978072 (Joe Perches      2010-01-13 09:31:44 -0800 1422)         @echo  '                    (requires a recent binutils and recent build (System.map))'
155ad605b3c9c (Sam Ravnborg     2005-07-07 17:56:08 -0700 1423)         @echo  '  dir/file.ko     - Build module including final link'

   (oh, look ...)

c4d5ee67ce265 (Robert P. J. Day 2009-04-24 12:35:23 -0400 1424)         @echo  '  modules_prepare - Set up for building external modules'
^1da177e4c3f4 (Linus Torvalds   2005-04-16 15:20:36 -0700 1425)         @echo  '  tags/TAGS       - Generate tags file for editors'
^1da177e4c3f4 (Linus Torvalds   2005-04-16 15:20:36 -0700 1426)         @echo  '  cscope          - Generate cscope index'
f4ed1009fcea8 (Jianbin Kang     2011-01-14 20:07:05 +0800 1427)         @echo  '  gtags           - Generate GNU GLOBAL index'
3f1d9a6cec011 (Michal Marek     2014-07-11 15:57:24 +0200 1428)         @echo  '  kernelrelease   - Output the release version string (use with make -s)'
3f1d9a6cec011 (Michal Marek     2014-07-11 15:57:24 +0200 1429)         @echo  '  kernelversion   - Output the version stored in Makefile (use with make -s)'
3f1d9a6cec011 (Michal Marek     2014-07-11 15:57:24 +0200 1430)         @echo  '  image_name      - Output the image name (use with make -s)'
$

Once you determine the offending line, you can examine its encompassing commit with git show:

$ git show c4d5ee67ce265
commit c4d5ee67ce26503d7eaf2aca5bb13c58e89d1be8
Author: Robert P. J. Day <rpjday@crashcourse.ca>
Date:   Fri Apr 24 12:35:23 2009 -0400

    kbuild: "make prepare" should be "make modules_prepare"
    
    Correct the Makefile help text to read "make modules_prepare".
    
    Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
    Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

diff --git a/Makefile b/Makefile
index b309fca4b944..b18afad2e100 100644
--- a/Makefile
+++ b/Makefile
@@ -1293,7 +1293,7 @@ help:
        @echo  '  dir/            - Build all files in dir and below'
        @echo  '  dir/file.[ois]  - Build specified target only'
        @echo  '  dir/file.ko     - Build module including final link'
-       @echo  '  prepare         - Set up for building external modules'
+       @echo  '  modules_prepare - Set up for building external modules'
        @echo  '  tags/TAGS       - Generate tags file for editors'
        @echo  '  cscope          - Generate cscope index'
        @echo  '  kernelrelease   - Output the release version string'

Some useful command-line options

A very small subset of options for git blame (there are far more):

-L <start>,<end>, -L :<funcname>
    Annotate only the given line range. May be specified multiple times.
    Overlapping ranges are allowed.

-s
    Suppress the author name and timestamp from the output.

-e, --show-email
    Show the author email instead of author name (Default: off).
    This can also be controlled via the ''blame.showEmail'' config option.

Some useful config options

From man git-config:

       blame.blankBoundary
           Show blank commit object name for boundary commits in git-
           blame(1). This option defaults to false.

       blame.coloring
           This determines the coloring scheme to be applied to blame
           output. It can be repeatedLines, highlightRecent, or none
           which is the default.

       blame.date
           Specifies the format used to output dates in git-blame(1).
           If unset the iso format is used. For supported values, see
           the discussion of the --date option at git-log(1).

       blame.showEmail
           Show the author email instead of author name in git-
           blame(1). This option defaults to false.

       blame.showRoot
           Do not treat root commits as boundaries in git-blame(1).
           This option defaults to false.
git_blame.1550919375.txt.gz · Last modified: 2019/02/23 10:56 by rpjday