Re: [PATCH v2 0/6] refs: excessive hook execution with packed refs

[Han-Wen Nienhuys <hanwen@google.com>]

On Fri, Jan 7, 2022 at 11:17 PM Junio C Hamano <gitster@pobox.com> wrote:
> > this is a resend of version 1 of this patch series to hopefully entice
> > some reviews. The only change is that v2 is rebased onto the current
> > main branch at commit e83ba647f7 (The seventh batch, 2022-01-05). The
> > following was from the orignial cover letter:
>
> I'll add Ævar, who has been making a lot of changes to the refs
> subsystem, and Han-Wen, whose work to add a new ref backend may need
> to interact with this change, as possible stake-holders to the CC list.

Thanks for the consideration, Jun. As the hook is called from refs.c,
it should not make a difference for reftable.

I looked over the patches. I didn't look at the bottom change to
packed/loose refs as I'm not an expert.

The individual transaction updates already support their own flags, so
this change generates some confusion. Consider:

int refs_delete_ref(struct ref_store *refs, const char *msg,
    const char *refname,
    const struct object_id *old_oid,
    unsigned int flags)

how would one delete a ref skipping the transaction hook? It will be
easy for someone to pass the SKIP_TRANSACTION_HOOK to
refs_delete_ref(), with surprising results.

It might make sense to not introduce a new flag namespace, but use
update->flags instead. You'd have to add your new flag after
REF_SKIP_REFNAME_VERIFICATION.
Bonus is that you can unittest the new flag using the existing
ref-store helper without extra work. (check that a transaction with &
without the flag works as expected.)

other than that, looks OK to me.

-- 
Han-Wen Nienhuys - Google Munich
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