From: Junio C Hamano <gitster@pobox.com>
Date: Tue, 17 Sep 2013 21:52:45 GMT
Subject: Re: [PATCH] diff: add a config option to control orderfile
Message-ID: <xmqqob7rw1xt.fsf@gitster.dls.corp.google.com>
In-Reply-To: <20130917205615.GA20178@sigill.intra.peff.net>

Jeff King <peff@peff.net> writes:

> I am mostly thinking of the problems we had with the "kup" tool, which
> expected stability across diffs that would be signed by both kernel.org.
> But as far as I know, they do not use patch-id. More details in case you
> are curious (including me arguing that we should not care, and it is
> kup's problem!) are here:
>
>   http://thread.gmane.org/gmane.comp.version-control.git/192331/focus=192424
>
> rerere is mentioned in that thread, but I believe that it does its own
> hash, and does not rely on patch-id.

It does not.  The reason rerere is relevant in that thread but is
not directly relevant here is because the thread is about changing
the diff algorithm, hence changing the common-sequence matches
between preimage and postimage, resulting in a different shape of
the conflicted section.  The hash rerere does still depends on the
patch text, but it is restricted to the conflicted region, so
whatever we do in patch-id will not affect it.  Also the rerere
database is not keyed by pathname (a conflict in _any_ file as long
as they have the same ours/theirs conflicted text is recognised as
the same conflict we have already seen), so changing the orderfile
would not affect it at all.