Add a test to t1091-sparse-checkout-builtin.sh that would result in an infinite loop and out-of-memory error before this change. The issue relies on having non-cone-mode patterns while trying to modify the patterns in cone-mode. The fix is simple, allowing us to break from the loop when the input path does not contain a slash, as the "dir" pattern we added does not. This is only a fix to the critical out-of-memory error. A better response to such a strange state will follow in a later change. Reported-by: Calbabreaker <calbabreaker@gmail.com> Helped-by: Taylor Blau <me@ttaylorr.com> Reviewed-by: Elijah Newren <newren@gmail.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>