From: Junio C Hamano Date: Wed, 11 Feb 2026 17:21:16 GMT Subject: Re: [PATCH] builtin/pack-objects: don't fetch objects when merging packs Message-ID: In-Reply-To: <20260211-pks-pack-objects-stdin-skip-backfill-fetch-v1-1-870cad56d8ae@pks.im> Patrick Steinhardt writes: > The "--stdin-packs" option can be used to merge objects from multiple > packfiles given via stdin into a new packfile. One big upside of this > option is that we don't have to perform a complete rev walk to enumerate > objects. Instead, we can simply enumerate all objects that are part of > the specified packfiles, which can be significantly faster in very large > repositories. > > There is one downside though: when we don't perform a rev walk we also > don't have a good way to learn about the respective object's names. As a > consequence, we cannot use the name hashes as a heuristic to get better > delta selection. > > We try to offset this downside though by performing a localized rev > walk: we queue all objects that we're about to repack as interesting, > and all objects from excluded packfiles as uninteresting. We then > perform a best-effort rev walk that allows us to fill in object names. > > There is one gotcha here though: when "--exclude-promisor-objects" has > not been given we will perform backfill fetches for any promised objects > that are missing. This used to not be an issue though as this option was > mutually exclusive with "--stdin-packs". But that has changed recently, > and starting with dcc9c7ef47 (builtin/repack: handle promisor packs with > geometric repacking, 2026-01-05) we will now repack promisor packs > during geometric compaction. The consequence is that a geometric repack > may now perform a bunch of backfill fetches. > > We of course cannot passe "--exclude-promisor-objects" to fix this > issue -- after all, the whole intent is to repack objects part of a > promisor pack. But arguably we don't have to: the rev walk is intended > as best effort, and we already configure it to ignore missing links to > other objects. So we can adapt the walk to unconditionally disable > fetching any missing objects. "passe" -> "pass". Other than that, very nicely described, and the implementation is surprisingly simple (thanks to a single global variable, and asumption that makes it safe to use such a single global variable, i.e., there is just one packing operation running at a time). Will queue. Thanks.