Re: [PATCH] fetch --prune: exit with error if pruning fails

> Hi Thomas,
>
> On Fri, 28 Jan 2022, Thomas Gummerer wrote:
>
>> Junio C Hamano writes:
>>
>> > Thomas Gummerer <t.gummerer@gmail.com> writes:
>> >
>> >> +test_expect_success REFFILES 'fetch --prune fails to delete branches' '
>> >> +	cd "$D" &&
>> >> +	git clone . prune-fail &&
>> >> +	cd prune-fail &&
>> >> +	git update-ref refs/remotes/origin/extrabranch main &&
>> >> +	>.git/packed-refs.new &&
>> >> +	test_must_fail git fetch --prune origin
>> >
>> > Is it because the lockfile ".new" on packed-refs prevents deletion
>> > of refs but does not block creation and updates to existing refs
>> > that it is an effective test for the "--prune" issue?  If we somehow
>> > "locked" the whole ref updates, then the fetch would fail even
>> > without "--prune", so it may be "effective", but smells like knowing
>> > too much implementation detail.  Yuck, but I do not offhand think of
>> > any better way (it is easier to think of worse ways), so without
>> > further input, I would say that this is the best (or "least bad") we
>> > can do.
>>
>> Yes, that's correct.  New refs will be created as loose refs, so they
>> don't care about packed-refs.  However deletions can potentially be
>> happening in packed-refs, and that's why it fails when 'packed-refs.new'
>> exists.
>>
>> I don't love the test either, but I also can't think of a better way to
>> do this.
>
> Maybe add a code comment about it? Something like:
>
> 	[...]
> 	: this will prevent --prune from locking packed-refs &&
> 	>.git/packed-refs.new &&
> 	[...]