Re: [PATCH v2] dir: check for single file cone patterns

Victoria Dye [off-list ref] writes:

This clearly explains the issue you're trying to fix: cone mode
sparse-checkout requires patterns like '/A/B/', !/A/B/*/', '/A/B/C/', etc.,
but invalid patterns like '/A/B/C' (no trailing slash) currently don't force
the switch to non-cone mode, leading to unexpected behavior.
...

quoted

To fix these issues, add a cone mode pattern check that asserts that
every pattern is either a directory match or the pattern '/*'. Add a
test to verify the new pattern check and modify another to reflect that
non-directory patterns are caught earlier.

I think this is the best way to maintain the current intended behavior of
cone mode sparse-checkout. While the idea of single file "exceptions" to
cone patterns has been brought up in the past (I think most recently at the
Contributor's Summit this past September [1]), it'd be a substantial change
that's definitely out-of-scope of this small bugfix.
...
And this test ensures the new check is working for the appropriate patterns.

This patch looks good to me, thanks for finding & fixing the bug!

Thanks for an excellently written review, and a patch that is well
done.

Will queue.