Re: [PATCH] fsck: ignore missing "refs" directory for linked worktrees

[Junio C Hamano <gitster@pobox.com>]

Patrick Steinhardt <ps@pks.im> writes:

> On Mon, Jun 02, 2025 at 10:53:50AM +0100, Phillip Wood wrote:
>> Hi Shejialuo
>> 
>> On 31/05/2025 04:39, shejialuo wrote:
>> > diff --git a/refs/files-backend.c b/refs/files-backend.c
>> > index 4d1f65a57a..bf6f89b1d1 100644
>> > --- a/refs/files-backend.c
>> > +++ b/refs/files-backend.c
>> > @@ -3762,6 +3762,9 @@ static int files_fsck_refs_dir(struct ref_store *ref_store,
>> >   	iter = dir_iterator_begin(sb.buf, 0);
>> >   	if (!iter) {
>> > +		if (errno == ENOENT && !is_main_worktree(wt))
>> > +			goto out;
>> > +
>> >   		ret = error_errno(_("cannot open directory %s"), sb.buf);
>> >   		goto out;
>> >   	}
>> 
>> I think it would be clearer to write this as
>> 
>> 	if (is_main_worktree(wt) || errno != ENOENT)
>> 		ret = error_errno(_("cannot open directory %s"), sb.buf);
>> 	goto out;
>> 
>> so that the condition that triggers the error message is explicit rather
>> than having to mentally invert the condition to figure out when we return an
>> error
>
> The downside though is that this mandates that `is_main_worktree()` must
> never set `errno` itself. So while it may be clearer, the original
> version feels safer to me.

FWIW, I found that the logic flow of the original more natural than
the proposed rewrite.  "dir_iterator_begin() appears to have failed
by not returning a usable iterator, so we may need to complain, but
as a special case, we can tolerate missing refs/ hierarchy if we are
not in the primary working tree." was how I read these three
additional lines.