Re: [PATCH] add boolean diff.suppress-blank-empty config option

From: Jim Meyering <meyering@gmail.com>
Date: Aug 16, 2008, 11:07 UTC
Message-ID: <loom.20080816T105522-117@post.gmane.org>
In-Reply-To: <7v4p5mb0a1.fsf@gitster.siamese.dyndns.org>

Junio C Hamano <gitster <at> pobox.com> writes:

Show 8 quoted lines

> Jim Meyering <jim <at> meyering.net> writes:
> > GNU diff's --suppress-blank-empty option makes it so that diff does not
> > add a space or tab before each empty output line of context.  With this
> > option, empty context lines are empty also in "git diff" output.
>
> AFAIK, ERN 103/120 inspired by your comment merely says an empty context
> is either an empty line or a line with a single space on it and does not
> deprecate the latter, more traditional, form (I do not know the current

This is not a POSIX compliance issue. Either format may be emitted.

> status of the update to the POSIX --- what's the recommended way to find
> it out by outsiders?)

Here's one copy of what's being added to the latest version of POSIX: http://www.opengroup.org/austin/aardvark/latest/xcubug2.txt Anyone can register (see Q2: http://www.opengroup.org/austin/faq.html) and then get the lastest draft, but it should be final (and hence public) pretty soon.

> We've hacked the patch application side to accomodate this special case to
> grok output from recent GNU diff already.  Can't we just stop at that,
> without having to do the same for generation side?  What's the downside of
> not doing so?

No pressure to add it to git. I deliberately did not propose that, based on the reception an earlier proposal received in this forum. I tried to make that clear in the header comments.

However, here's why I use this patch:
  - there are many contexts where I try to avoid trailing blanks, and
    eliminating spurious ones makes it easier to spot possibly-problematic ones.
  - I version-control some diff output, and having diff-generating programs
    handle the elimination of unnecessary trailing blanks is slightly safer
    than doing it from each context.
  - some tools systematically remove or highlight trailing blanks.  If I can
    make my diff output less susceptible with such an option, I'll use it.

Bottom line, it doesn't really matter. I posted the patch in case someone else would find it useful.