Re: branch description

From: Junio C Hamano <gitster@pobox.com>
Date: Apr 19, 2008, 17:43 UTC
Message-ID: <7v1w51g2q5.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <200804191118.50105.johan@herland.net>

Johan Herland <johan@herland.net> writes:

> The problem with (3) vs. (4) is that in (3) we must make sure that whenever
> a branch is moved/renamed (e.g. "git clone", "git branch -m", probably more
> as well), the corresponding description is moved/renamed as well. This is
> elegantly solved in (4).

If your "elegently solved" is coming from an assumption that it is enough for "git mv" (for example) to just copy whatever is in .git/refs/heads/foo to .git/refs/heads/bar without understanding what is contained in it, that assumption unfortunately does not hold.

You must support packed refs, so you need to teach the refs infrastructure what per-branch attributes there are other than the commit object name it points at anyway.

And we already do -- when you do "branch -m foo bar", corresponding config entries are also renamed. We also move reflogs.

A possible approach that would work, which contains elements from (4), is to change implementations of loose ref to have this extra info in loose ref files (that is what (4) is), *and* introduce another separate mechanism to store corresponding information for packed refs elsewhere. Propagation needs to deal with both representations, renaming needs to deal with both representations, looking up needs to deal with both representations, everybody needs to deal with both representations.

If you are going to invent "another separate mechanism" to support packed refs anyway, why not use that same mechanism to record information for loose ones as well? That is the approach suggested by (3). In either way we need to teach relevant parts of the code for propagation, renaming, looking up etc about the new mechanism.