Re: cvs import

From: Michael Haggerty <mhagger@alum.mit.edu>
Date: Sep 14, 2006, 04:17 UTC
Message-ID: <4508D7DA.8000302@alum.mit.edu>
In-Reply-To: <46a038f90609131416s1a53b53xd12c3661140fec7a@mail.gmail.com>

Martin Langhoff wrote:

Show 22 quoted lines

> On 9/14/06, Markus Schiltknecht <markus@bluegap.ch> wrote:
>> Martin Langhoff wrote:
>> > On 9/14/06, Jon Smirl <jonsmirl@gmail.com> wrote:
>> >> Let's copy the git list too and maybe we can come up with one importer
>> >> for everyone.
>> >
>> > It's a really good idea. cvsps has been for a while a (limited, buggy)
>> > attempt at that. One thing that bothers me in the cvs2svn algorithm is
>> > that is not stable in its decisions about where the branching point is
>> > -- run the import twice at different times and it may tell you that
>> > the branching point has moved.
>>
>> Huh? Really? Why is that? I don't see reasons for such a thing happening
>> when studying the algorithm.
>>
>> For sure the proposed dependency-resolving algorithm which does not rely
>> on timestamps does not have that problem.
> 
> IIRC, it places branch tags as late as possible. I haven't looked at
> it in detail, but an import immediately after the first commit against
> the branch may yield a different branchpoint from the same import done
> a bit later.

This is correct. And IMO it makes sense from the standpoint of an all-at-once conversion.

But I was under the impression that this wouldn't matter for content-indexed-based SCMs. The content of all possible branching points is identical, and therefore from your point of view the topology should be the same, no?

But aside from this point, I think an intrinsic part of implementing incremental conversion is "convert the subsequent changes to the CVS repository *subject to the constraints* imposed by decisions made in earlier conversion runs. And the real trick is that things can be done in CVS (e.g., line-end changes, manual copying of files in the repo) that (a) are unversioned and (b) have retroactive effects that go arbitrarily far back in time. This is the reason that I am pessimistic that incremental conversion will ever work robustly.

Michael