Subject: Re: breakage in revision traversal with pathspec

From: Junio C Hamano <[email-masked]>
Date: Tue, 10 Sep 2013 15:23:50 -0700

Kevin Bracey <[email-masked]> writes:

> On 10/09/2013 20:19, Junio C Hamano wrote:
>> I am grumpy X-<.
>>
>> It appears that we introduced a large breakage during 1.8.4 cycle to
>> the revision traversal machinery and made pathspec-limited "git log"
>> pretty much useless.
>>
>> This command
>>
>>      $ git log v1.8.3.1..v1.8.4 -- git-cvsserver.perl
>>
>> reports that a merge 766f0f8ef7 (which did not touch the specified
>> path at all) touches it.
>>
>> Bisecting points at d0af663e (revision.c: Make --full-history
>> consider more merges, 2013-05-16).
>>
> That merge appearing *with* --full-history would seem like correct
> behaviour to me. Or at least it's what I intended.

Oh, of course.  "--full-history" is about showing any pointless
change, "the mainline was a lot more up-to-date and there were
changes relative to a fork based on an older baseline", so your
updated "log" should show that in the mainline git-cvsserver.perl
has been more fresh when that merge happened.  But it shouldn't
appear if the user does not ask for "--full-history".

> However, your particular example occurs *without*--full-history, which
> suggests a problem.

Yes.

> I note that "gitk v1.8.3^0..v1.8.4" and "git log --parents
> v1.8.3..v1.8.4" show that merge in Git 1.8.3, but not in Git 1.8.4. So
> we're going partially forwards, at least.

With the testcases demonstrating the cases your series fixed that
all look sensible, I think it is not really an option for us to
revert them; you do not have to defend it with "we are going
partially forwards" ;-).