From: Junio C Hamano <gitster@pobox.com>
Date: Wed, 21 Apr 2010 09:04:37 GMT
Subject: Re: [PATCH] revision: --ancestry-path
Message-ID: <7vy6ghb2hm.fsf@alter.siamese.dyndns.org>
In-Reply-To: <201004211046.22643.johan@herland.net>

Johan Herland <johan@herland.net> writes:

> I'm not very familiar with "rewrite_parents", nor do I know exactly how it 
> should affect/interoperate with --ancestry-path in all cases, but running
>
> 	git rev-list D..M -- M.t
>
> produces one commit (M), whereas
>
> 	git rev-list --ancestry-path D..M -- M.t
>
> produces nothing, so I suspect there is something not quite right here.

Merge simplification gets in our way big time.

          D---E-------F
         /     \       \
    B---C---G---H---I---J
   /                     \
  A-------K---------------L--M

While traversing the history from M, we notice that M's parent is L, and
then further we notice that neither the transition between J to L nor
between K to L change the named path M.t, so we simplify the merge L to
have K as its sole parent.  This makes M appear disconnected from D's
decendant chain, and causes the TMP_MARK reverse traversal not to work as
intended.