Re: [PATCH 4/6] introduce a commit metapack

[Jeff King <peff@peff.net>]

On Tue, Jan 29, 2013 at 11:17:41PM -0800, Junio C Hamano wrote:

> > True, but it is even less headache if the file is totally separate and
> > optional.
> 
> Once you start thinking about using an offset to some list of SHA-1,
> perhaps?  A section inside the same file can never go out of sync.

Yes, having a data dependency is important. It is unavoidable to have a
dependency on the packfile, though (and that is why the index and the
metapacks embed the sha1 of the packfile). If the offsets used are
packfile offsets, then that is sufficient.

If the offsets are from the index, then yes, putting it in the same file
is one way to keep them tied together. Another way is to do the same
sha1 verification, except to embed the sha1 of the index in the
metapack.

So I certainly consider putting the dependency-handling to be a point in
favor of the same file, but I'd weight it against other points (headache
of bumping index version, performance of both types, etc).

> Also a longer-term advantage is that you can teach index-pack to do
> this.

I think that is roughly the same amount of difficulty to do whether they
are in the same file or not.

-Peff