Re: Bug report - sparse-checkout ignores prefix when run in subdirectories

[Derrick Stolee <stolee@gmail.com>]

On 1/5/2022 6:19 PM, Elijah Newren wrote:
> On Wed, Jan 5, 2022 at 2:38 PM Junio C Hamano <gitster@pobox.com> wrote:
>>
>> Lessley Dennington <lessleydennington@gmail.com> writes:
>>
>>> Hello everyone! See the following bug report pertaining to sparse-checkout
>>> when run outside top-level directories.
>>
>> In a bug report it is fine, but "outside top-level" usually means
>> above the top-level of the working tree.  Here, I think you meant
>> running in a subdirectory of the top-level.
>>
>> Perhaps something along this line?
>>
>>  builtin/sparse-checkout.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git c/builtin/sparse-checkout.c w/builtin/sparse-checkout.c
>> index 45e838d8f8..4e5efbb85e 100644
>> --- c/builtin/sparse-checkout.c
>> +++ w/builtin/sparse-checkout.c
>> @@ -753,6 +753,16 @@ static int sparse_checkout_set(int argc, const char **argv, const char *prefix)
>>         if (!core_sparse_checkout_cone && argc == 0) {
>>                 argv = default_patterns;
>>                 argc = default_patterns_nr;
>> +       } else if (argc && prefix && *prefix) {
>> +               /*
>> +                * The args are not pathspecs, so unfortunately we
>> +                * cannot imitate how cmd_add() uses parse_pathspec().
>> +                */
>> +               int i;
>> +               int prefix_len = strlen(prefix);
>> +
>> +               for (i = 0; i < argc; i++)
>> +                       argv[i] = prefix_path(prefix, prefix_len, argv[i]);
>>         }
> 
> This looks good (sparse_checkout_add() needs a similar fix), at least
> for cone mode.  There might be a small pickle here that I didn't think
> about before.  --cone mode always uses directories, so we expect
> people to provide directory names.  Because of that, I think it's fair
> to expect the arguments passed to `set` or `add` to be paths relative
> to the current working directory.  In contrast, for non-cone mode we
> do not expect pathnames but gitignore-style globs.  And when we get
> gitignore-style globs, we don't know if they were intended relative to
> the current working directory or the toplevel, because we only have
> one $GIT_DIR/info/sparse-checkout file versus many .gitignore files.
> So, should "**.py" go directly into the sparse-checkout file as-is, or
> be translated to "my/current/subdir/**.py" first?
> 
> Maybe translating is always fine, or maybe we want to throw an error
> when: (not using cone mode and prefix is non-empty and any patterns
> are provided).
> 
> Thoughts?

You seem to have worked it out in the other threads, but I came here
to agree: we should not do this transformation unless we are in
cone mode. We should also do this when "--cone" is supplied.

The prefix_path() collapses "../" entries, right? Just making sure
that we test that scenario when writing a full fix here.

For example, if we added a case to t1092, we should be able to
do the following within any of the example repos:

	git sparse-checkout disable &&
	cd folder1 &&
	git sparse-checkout set --cone . ../folder2
	git sparse-checkout list >actual &&
	cat >expect <<-EOF &&
	folder1
	folder2
	EOF
	test_cmp expect actual

Thanks,
-Stolee