On 2021-08-30 at 00:43:30, Taylor Blau wrote:
> On Sun, Aug 29, 2021 at 05:34:18PM -0700, Junio C Hamano wrote:
> > Taylor Blau <me@ttaylorr.com> writes:
> >
> > > now or later would affect this series. Even if we just disallow
> > > --object-dir pointing at a non-alternate repository, we would still have
> > > the issue of having alternate chains which don't all have the same
> > > object format.
> >
> > Exactly.  That is why I feel that it probably needs to be dealt with
> > before doing anything else.  The alternate mechanism pulling in an
> > object store that uses incompatible hash algo would break not just
> > the multi-pack-index but probably the basic object access layer as
> > well, which would be more grave problem, no?
> 
> Yeah; it does. Maybe I'm holding it wrong (and brian, cc'd, can help
> me), but this is an easy way to see the problem:
> 
>   git init repo
>   git init alternate
> 
>   git -C repo commit --allow-empty -m foo
>   ( cd repo/.git/objects && pwd ) >alternate/.git/objects/info/alternates
>   git -C alternate rev-list --objects --alternate-refs
> 
> which will produce:
> 
>     $ git rev-list --objects --alternate-refs
>     warning: invalid line while parsing alternate refs: <sha256 id>
> 
> But I don't know if I quite understand your "probably needs to be dealt
> with before doing anything else". I think we can proceed with this
> series and deal with the alternate object-format thing separately, no?

Yeah, this is a possible problem.  You can also see it when using git
index-pack outside of a repository with an incorrect --object-format
option.

I'm not sure how folks want to deal with that; I'm just fine saying,
"Well, don't do that," but other folks may have different opinions.
-- 
brian m. carlson (he/him or they/them)
Toronto, Ontario, CA