Re: Patchdiff

From: Junio C Hamano <gitster@pobox.com>
Date: Jan 27, 2010, 01:30 UTC
Message-ID: <7vzl40wcz2.fsf@alter.siamese.dyndns.org>
In-Reply-To: <alpine.LFD.2.00.1001262014250.1681@xanadu.home>

Nicolas Pitre <nico@fluxnic.net> writes:

Show 11 quoted lines

>> Do we have anything that allows me to compare two versions of a patch?
>> In theory it'd do something like "apply both patches to the their
>> merge base, then show the diff between the results". I don't think we
>> have something like that, since there's probably some major caveats
>> about conflicts when applying the patches to their merge-base. Or
>> perhaps my theory is silly, and there's an easier way to compare two
>> patches (other than looking at a diff's diff, which I've never been
>> good at).
>
> What about Git's diff -c/--cc ?  You'd have to reverse the parenthood 
> logic though.

When I did "diff --cc" originally, I thought about its interaction with reverse (-R), and gave up.

The thing is, "--cc" output needs to show "here is _the_ end result", together with "and each sides did things in these different ways (shown with +/- annotations)".

When showing a merge, there is one end result (the merged version), so it fits the model that is a natural extension of two-way diff. In the "two patches walked in a bar, modified the same version and produced two different results" case, the common thing is the preimage, not postimage. I couldn't come up with a combined output format that visually makes sense for that mode of operation.