Re: [PATCH v3 0/2] grep.c: teach --only-matching to 'git-grep(1)'

From: Jeff King <peff@peff.net>
Date: Jul 6, 2018, 20:33 UTC
Message-ID: <20180706203339.GB4648@sigill.intra.peff.net>
In-Reply-To: <20180706201522.GA657@syl.attlocal.net>

On Fri, Jul 06, 2018 at 03:15:22PM -0500, Taylor Blau wrote:

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> On Fri, Jul 06, 2018 at 11:21:06AM -0700, Junio C Hamano wrote:
> > Taylor Blau <me@ttaylorr.com> writes:
> >
> > > I think that this might be clear enough on its own, especially since
> > > this is the same as BSD grep on my machine. I think that part_s_ of a
> > > line indicates that behavior, but perhaps not. On GNU grep, this is:
> > >
> > >   Print only the matched (non-empty) parts of a matching line, with each
> > >   such part on a separate output line.
> >
> > Interesting.  I wonder what "git grep -o '^'" would do ;-)
> 
> That invocation prints nothing, but on BSD grep it prints quite a few
> blank lines :-).
> 
> I'm hesitant on sending a patch per the hunk of your reply below because
> of this. Should we mirror BSD grep's behavior exactly here? I suppose
> that we could somehow, but it seems like we might be doing too much to
> support what appears to me to be an odd use-case.

IMHO the GNU behavior (omitting non-empty matches) makes more sense. And it's also what your patch already does. ;)

Although amusingly "git grep -o ^" will still print a ton of "Binary file ... matches". That _also_ matches what GNU grep does. I'm not sure if there's a saner behavior (it really has nothing to do with the funny empty match; any binary file with -o cannot show the normal text line).

Show 6 quoted lines

> > In any case, I find that the GNU phrasing is the most clear among
> > the ones I've seen in this thread so far.
> 
> OK. I'm happy to re-send that patch with the GNU phrasing depending on
> what others think (and the above). I'll let this cook and collect some
> thoughts over the weekend.

FWIW, I like the GNU phrasing. I thought the "non-empty" part was not all that interesting, but after hearing that BSD behaves differently, it is probably worth mentioning.

I think the actual behavior of your patch matches GNU grep, and does not need changing.

-Peff