Re: [PATCH] Add diff.context option to specify default context

[Junio C Hamano <gitster@pobox.com>]

Jeff Muizelaar <jmuizelaar@mozilla.com> writes:

> This adds a diff.context config option to allow specifying
> the number of lines of context. This is similar to Mercurial's
> 'unified' option.

Random thoughts.

* Please refer to Documentation/SubmittingPatches.  Saving your
  message in a mbox and applying it would produce this crap:

    commit ba4c972eacb91058f1317dbcd4ff77b471fa938e
    Author: Jeff Muizelaar <jmuizelaar@mozilla.com>
    Date:   Fri Sep 14 14:16:03 2012 -0400

        Add diff.context option to specify default context

        This adds a diff.context config option to allow specifying
        the number of lines of context. This is similar to Mercurial's
        'unified' option.

        commit 1bd81c75de6824c39852bc8516acd0733737ed83
        Author: Jeff Muizelaar <jmuizelaar@mozilla.com>
        Date:   Fri Sep 14 13:55:02 2012 -0400

            [PATCH] Add diff.context option to specify default context

            This adds a diff.context config option to allow specifying
            the number of lines of context. This is similar to
            Mercurial's
            'unified' option.

  which is not acceptable.

* Sign-off your patch.

* Citing similaritly to options in other systems does not add much
  value for people who read the proposed log message.  In this case,
  I think the first sentence is written clearly enough that it is
  sufficient without such clarification.  If anything, it should
  instead say:

	diff: diff.context configuration gives default to -U

	Introduce a configuration variable diff.context that tells
	Porcelain commands to use a non-default number of context
	lines instead of 3 (the default).  With this variable, users
	do not have to keep repeating "git log -U8" from the command
	line; instead, it becomes sufficient to say "git config
	diff.context 8" just once.

  or something like that to make it clear that it is related to our
  -U option.

* That relationship with the -U option may worth mentioning in the
  documentation, not just in the log message.

* The configuration is read only in diff_ui_config and not in the
  lower-level diff_config.  What the patch does is the right thing.

  It however needs to be documented in the patch to diff-config.txt
  that it affects only the Porcelain commands, and does not break
  plumbing commands.

* Tests?  Minimally, the cases you may want to check are:

  - What happens with various values set to this variable, and does
    the code properly diagnose errors?

    [diff]
	context ;# boolean?
        context = no
        context = 0
        context = -1
        context = 8

  - What happens when the variable is set and the command line gives
    a different value with -U?

    git config diff.context 8
    git log -U4 -1

  - Does it really keep plumbing intact?

    git config diff.context 8
    git diff-files -p


Thanks.