From: William Sprent <williams@unity3d.com>
To: Elijah Newren <newren@gmail.com>,
William Sprent via GitGitGadget <gitgitgadget@gmail.com>
Cc: Git Mailing List <git@vger.kernel.org>,
Johannes Schindelin <Johannes.Schindelin@gmx.de>
Subject: Re: [PATCH] fast-export: fix surprising behavior with --first-parent
Date: Wed, 24 Nov 2021 14:05:28 +0100 [thread overview]
Message-ID: <96bba3dd-589c-dc37-012a-6c827cafacb8@unity3d.com> (raw)
In-Reply-To: <CABPp-BGm0VtU=z0r0oGc48J020Meh_xdibnagNeDmBGQ-RVu+g@mail.gmail.com>
On 23/11/2021 20.14, Elijah Newren wrote:
> On Tue, Nov 23, 2021 at 5:25 AM William Sprent via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
>>
>> From: William Sprent <williams@unity3d.com>
>> ...
>
> Wow, interesting. I did some related work that I never submitted at
> https://github.com/newren/git/commit/08f799b4667de1c755c78e1ea1657f946b588556
> -- in that commit, I also noticed that fast-export did not seem
> careful enough about making sure to process all commits, and came up
> with a much different fix. However, in my case, I didn't know how to
> trigger the problems in fast-export without some additional changes I
> was trying to make, and since I never got those other changes working,
> I didn't think it was worth submitting my fix. My solution is more
> complex, in part because it was designed to handle ordering
> requirements & recommendations other than just ancestry. However, we
> don't currently have any additional ordering requirements (the current
> code only considers ancestry), so your solution is much simpler. If I
> do at some point get my other changes working, I'd need to
> re-introduce the queue and handle_tail() and my changes to these, but
> that can always be done later if and when I get those other changes
> working.
>
Ah that is interesting. Good to know. I was happy that I could make
fast-export rely on revision.c for ordering. At surface level, with the
minimal amount of insight I have, that seems like an alright separation
of concerns.
> Interestingly, Dscho added both the --reverse ability to revision.c
> and the commits object_array and the handle_tail() stuff in
> fast-export.c. Both were done in the same year, and --reverse came
> first. See 9c5e66e97da8 (Teach revision machinery about --reverse,
> 2007-01-20) and f2dc849e9c5f (Add 'git fast-export', the sister of
> 'git fast-import', 2007-12-02). It's not clear why revs.reverse = 1
> wasn't used previously, although it certainly didn't occur to me
> either and I think it would have been an alternative solution to my
> first ever git.git contribution -- 784f8affe4df (fast-export: ensure
> we traverse commits in topological order, 2009-02-10). (Though
> rev.reverse = 1 wouldn't have provided the same speedups that
> rev.topo_order=1 provided.)
Ah. Thanks for the insight.
> I can't think of any cases where this would cause any problems, and it
> seems like using rev.reverse is a pretty clean solution. Just in case
> I'm missing something, though, it would be nice to get Dscho to also
> comment on this. I'm cc'ing him.
Thanks. Good idea.
next prev parent reply other threads:[~2021-11-24 14:29 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-23 11:28 [PATCH] fast-export: fix surprising behavior with --first-parent William Sprent via GitGitGadget
2021-11-23 13:07 ` Ævar Arnfjörð Bjarmason
2021-11-24 11:57 ` William Sprent
2021-11-23 19:14 ` Elijah Newren
2021-11-24 13:05 ` William Sprent [this message]
2021-11-24 0:41 ` Junio C Hamano
2021-11-24 13:05 ` William Sprent
2021-12-09 8:13 ` [PATCH v2] " William Sprent via GitGitGadget
2021-12-10 3:48 ` Elijah Newren
2021-12-10 21:55 ` Junio C Hamano
2021-12-10 22:02 ` Elijah Newren
2021-12-13 15:09 ` William Sprent
2021-12-14 0:31 ` Elijah Newren
2021-12-14 13:11 ` William Sprent
2021-12-16 16:23 ` [PATCH v3] " William Sprent via GitGitGadget
2021-12-21 18:47 ` Elijah Newren
2021-12-21 20:50 ` Junio C Hamano
2021-12-22 8:38 ` William Sprent
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