Re: [PATCH] t3400 (rebase): add failing test for a peculiar rev spec

From: Junio C Hamano <gitster@pobox.com>
Date: Apr 19, 2013, 16:21 UTC
Message-ID: <7vvc7i330b.fsf@alter.siamese.dyndns.org>
In-Reply-To: <CALkWK0=RDCCSxOJ2TU4=tniSRTg9VJohJ8Pf6uN9E=fd3jg=_Q@mail.gmail.com>

Ramkumar Ramachandra <artagnon@gmail.com> writes:

> I'm more interested in knowing what you think of my first point: is
> :/text fundamentally broken, as it can't be combined with other
> operators like the other rev specs can?  If so, how do you think we
> should fix it?

The question :/string wants to ask is fundamentally ambiguous once you start wanting to give arbitrary string to it.

Think what this asks:

    git show ":/Fix regression introduced by commit v1.5.1-rc1"~113^2

Is it looking for a commit that fixes v1.5.1-rc1 and then locate the side branch that waas merged by the 113th-generation parent of that fix? Or is it looking for the commit that fixes v1.5.1-rc1~113^2?

When we introduced a postfix $rev^{/string} operator at 32574b68c57f (get_sha1: support $commit^{/regex} syntax, 2010-12-13) to dig from a given rev, we designed it so that we can disambiguate between the two: HEAD^{/Fix v1.5.1~113^2} vs HEAD^{/Fix v1.5.1}~113^2.

But the tradeoff made with 28a4d9404438 (object name: introduce ':/<oneline prefix>' notation, 2007-02-24), which is much older than the $rev^{/string} syntax, is to help casual interactive use by not requiring sometimes-hard-to-type line noise characters.

Even back then, I did not want to paint us into a corner we cannot escape from, and made sure the syntax has an escape hatch built-in.

cf.

  http://thread.gmane.org/gmane.comp.version-control.git/40460/focus=40477

If you cared deeply enough, you could activate it, to take something like:

    git show ":/!(s=Fix regression by v1.5.1-rc1~113^2)~20"

to say "The 20th-generation parent of the commit whose subject says it fixed regression at v1.5.1-rc1~113^2".

That would make this

	":/!(a=Ramkumar)(s=move diff.wordRegex)~4"

a way to find the fourth-generation parent of 2ead7a674d7f (t5516 (fetch-push): update test description, 2013-04-02) as a natural extension, I guess.