What makes a good Git commit?

Links:

• Commit Message Guidelines
• OpenStack advice
• Chris Beams' advice
• Stack Overflow advice
• SlideShare presentation

Any other good ones?

• Subject (first) line:
  • 60 characters or less for pretty-printing (git log --oneline)
  • Be accurate
  • Include subsystem name at front if possible
  • Use the imperative mood
  • No ending period
• Commits themselves:
  • Well-defined and modular, for future cherry picking or reverting.
  • Complete; use git commit --amend to assure this.
• Commit messages:
  • What is being changed, what functionality is being affected (if any).
  • Why it is being changed.
  • References to discussions about this commit (people, mailing lists).
  • Level of testing this commit has had.
  • Names of others who have ACKed/tested/reviewed this commit.
  • References to bug tracker items (JIRA) this commit is addressing.

$ git show --summary 6ff005cf19363382fc867d7876a75fd8a386e894
commit 6ff005cf19363382fc867d7876a75fd8a386e894
Author: Dave Prue <dave@prue.com>
Date:   Thu Aug 31 19:21:01 2017 +0200

    sunxi: Fix CONFIG_SUNXI_GMAC references
    
    SUNXI_GMAC was still used to configure the code where as the
    same has been renamed and moved to Kconfig in below commit
    "sunxi: Move SUNXI_GMAC to Kconfig"
    (sha1: 4d43d065db3262f9a9918ba72457bf36dfb8e0bb)
    
    Signed-off-by: Dave Prue <dave@prue.com>
    Reviewed-by: Simon Glass <sjg@chromium.org>
    Reviewed-by: Jagan Teki <jagan@openedev.com>
    Reviewed-by: Mark Kettenis <kettenis@openbsd.org>
    Tested-by: Mark Kettenis <kettenis@openbsd.org>
    [Tweek commit message, config_whitelist.txt, build-whitelist.sh]
    Signed-off-by: Jagan Teki <jagan@openedev.com>

If several files are being touched, use git diff --stat to generate a summary, and add that info to the commit message. Even if you don't add this to the commit message, you can see it later with git show --stat:

$ git show --stat 6ff005cf19363382fc867d7876a75fd8a386e894
commit 6ff005cf19363382fc867d7876a75fd8a386e894
Author: Dave Prue <dave@prue.com>
Date:   Thu Aug 31 19:21:01 2017 +0200

    sunxi: Fix CONFIG_SUNXI_GMAC references
    
    SUNXI_GMAC was still used to configure the code where as the
    same has been renamed and moved to Kconfig in below commit
    "sunxi: Move SUNXI_GMAC to Kconfig"
    (sha1: 4d43d065db3262f9a9918ba72457bf36dfb8e0bb)
    
    Signed-off-by: Dave Prue <dave@prue.com>
    Reviewed-by: Simon Glass <sjg@chromium.org>
    Reviewed-by: Jagan Teki <jagan@openedev.com>
    Reviewed-by: Mark Kettenis <kettenis@openbsd.org>
    Tested-by: Mark Kettenis <kettenis@openbsd.org>
    [Tweek commit message, config_whitelist.txt, build-whitelist.sh]
    Signed-off-by: Jagan Teki <jagan@openedev.com>

 arch/arm/include/asm/arch-sunxi/sys_proto.h | 2 +-
 board/sunxi/Makefile                        | 2 +-
 include/configs/sunxi-common.h              | 2 +-
 scripts/build-whitelist.sh                  | 4 ++--
 scripts/config_whitelist.txt                | 1 -
 5 files changed, 5 insertions(+), 6 deletions(-)
$