Re: [PATCH RESEND] branch: allow deleting dangling branches with --force

["René Scharfe" <l.s.r@web.de>]

Am 26.08.21 um 01:28 schrieb Ævar Arnfjörð Bjarmason:
>
> On Wed, Aug 25 2021, Junio C Hamano wrote:
>
>> René Scharfe <l.s.r@web.de> writes:
>>
>>> git branch only allows deleting branches that point to valid commits.
>>> Skip that check if --force is given, as the caller is indicating with
>>> it that they know what they are doing and accept the consequences.
>>> This allows deleting dangling branches, which previously had to be
>>> reset to a valid start-point using --force first.
>>>
>>> Signed-off-by: René Scharfe <l.s.r@web.de>
>>> ---
>>> Original submission:
>>> http://public-inbox.org/git/52847a99-db7c-9634-b3b1-fd9b1342bc32@web.de/
>>
>> Thanks.
>>
>>> +test_expect_success 'branch --delete --force removes dangling branch' '
>>> +	test_when_finished "rm -f .git/refs/heads/dangling" &&
>>> +	echo $ZERO_OID >.git/refs/heads/dangling &&
>>> +	git branch --delete --force dangling &&
>>> +	test_path_is_missing .git/refs/heads/dangling
>>> +'
>>
>> This goes against the spirit of the series merged at c9780bb2 (Merge
>> branch 'hn/prep-tests-for-reftable', 2021-07-13).
>>
>> Can we creat the dangling ref and test the lack of "dangling" ref in
>> the end in a less transparent way?
>>
>> An escape hatch is to make this test depend on the REFFILES
>> prerequisite, just like dc474899 (t4202: mark bogus head hash test
>> with REFFILES, 2021-05-31) did, which may be more appropriate.
>
> I'm not sure, but this may also be a good example of the sort of thing
> that we should probably go beyond REFFILES with, i.e. is it even
> possible under reftable to run into this sort of situation?

Probably yes: A commit can disappear when its object file or pack or
alternate object database gets lost somehow, and a ref store could
only compensate for that loss if it kept a copy of the ref target,
which seems impractical.

René