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Re: [PATCH 06/14] packfile: express constants in terms of the_hash_algo




On Tue, Oct 9, 2018 at 3:25 PM brian m. carlson
<sandals@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Mon, Oct 08, 2018 at 03:59:36PM -0700, Stefan Beller wrote:
> > On Mon, Oct 8, 2018 at 2:57 PM brian m. carlson
> > <sandals@xxxxxxxxxxxxxxxxxxxx> wrote:
> > >
> > > Replace uses of GIT_SHA1_RAWSZ with references to the_hash_algo to avoid
> > > dependence on a particular hash length.
> >
> > Unlike the previous patches, this is dealing directly with packfiles,
> > which (I would think) carry their own hash function selector?
> > (i.e. packfiles up to version 4 are sha1 hardcoded and version
> > 5 and onwards will have a hash type field. Usually that hash type would
> > match what is in the_repository, but you could obtain packfiles
> > out of band, or the translation table that we plan to have might
> > be part of the packfile/idx file?)
>
> Yeah, the transition plan doesn't specify a format for pack files, but
> we may end up needing one.  We definitely have a specified format for
> index files already, and that's where the translation table will be.
> Anything other than the pack index and the loose object index in the
> .git directory will have the same algorithm as the rest of the
> repository, so technically we could use any pack format as long as it
> lives in the .git directory.
>
> This code is mostly here on an interim basis to let us compile with a
> fully SHA-256 (no SHA-1) Git.  Once that piece is done, we can move on
> to a stage 4 Git, which can do either only SHA-256, or only SHA-1, where
> we'll learn about various pack file formats and detecting the algorithm
> from them.

This second paragraph really helps to put things into perspective, thanks!
I assume this interim base of code only applies to this patch?
(In that case maybe put it into the commit message?)