Re: [PATCH] fetch: commit references fetched before backfilling tags

> On Fri, Oct 09, 2026 at 12:10:37AM +0200, Karthik Nayak wrote:
> > In 0e358de64a (fetch: use batched reference updates, 2025-05-19), the
> > fetch code was modified to use batched updates to provide a good
> > performance improvement. Wherein batched updates were used to fetch both
> > references and backfill tags.
> > 
> > When using batched updates, the references aren't yet committed to disk
> > when we start backfilling tags. This means in situations such as shallow
> > fetching the negotiation during backfilling tags, the client doesn't
> > have any references to report in the 'have' section. Since backfilling
> > doesn't use a depth limit, this can cause the server to send all the
> > objects present in the repository.
> 
> So in my own words: the server sends the reference, we queue them in a
> transaction, but don't commit it yet. We then try to backfill tags, and
> because we don't have the refs committed yet the backfill will think we
> don't have any of the relevant commits that those tags point to.
> Consequently, the packfile negotiation will result in way more objects
> being fetched than necessary.
> 
> This makes me wonder why we even do a proper fetch. In theory, we could
> basically just ask the server for the individual tagged objects without
> performing any negotiation, right?
> 
> Or... well, would that work with nested annotated tags? No idea.