Re: [PATCH v4 05/25] midx: clear auxiliary .rev after replacing the MIDX

From: Taylor Blau <me@ttaylorr.com>
Date: Aug 30, 2021, 00:43 UTC
Message-ID: <YSwpsp/hQsPFnj+I@nand.local>
In-Reply-To: <xmqqfsur7otx.fsf@gitster.g>

On Sun, Aug 29, 2021 at 05:34:18PM -0700, Junio C Hamano wrote:

Show 12 quoted lines

> 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?

Thanks, Taylor