From: Jeff King <peff@peff.net>
Date: Wed, 27 Mar 2024 08:37:25 GMT
Subject: Re: [PATCH 11/11] midx-write.c: use `--stdin-packs` when repacking
Message-ID: <20240327083725.GC830163@coredump.intra.peff.net>
In-Reply-To: <736be63234baf7fc6df8259d9bb7298858b2bc74.1711387439.git.me@ttaylorr.com>

On Mon, Mar 25, 2024 at 01:24:50PM -0400, Taylor Blau wrote:

> Though correct, this typically yields a poorly structured pack, since
> providing the objects list over stdin does not give pack-objects a
> chance to discover the namehash values for each object, leading to
> sub-optimal delta selection.
> 
> We can use `--stdin-packs` instead, which has a couple of benefits:
> 
>   - it does a supplemental walk over objects in the supplied list of
>     packs to discover their namehash, leading to higher-quality delta
>     selection
> 
>   - it requires us to list far less data over stdin; instead of listing
>     each object in the resulting pack, we need only list the
>     constituent packs from which those objects were selected in the MIDX

Yeah, using --stdin-packs makes much more sense to me. I have to admit
that I do not really see the point "multi-pack-index repack" in the
first place. You'd presumably be better off with geometric repacking,
and I think "repack --geometric --write-midx" will do things in the
right order (new pack, then write midx, then delete redundant packs).

I guess "multi-pack-index repack" came before geometric repacking, and
is maybe redundant-ish now? If that's the case, then I guess I don't
care that much about optimizing its packs. ;) But we can't really delete
it without a deprecation period, so making it more sensible in the
meantime is reasonable to me.

-Peff