Previously, `parse_pathspec_file()` was tested indirectly by invoking
git commands with properly crafted inputs. As demonstrated by the
previous bugfix, testing complicated black boxes indirectly can lead to
tests that silently test the wrong thing.
Introduce direct tests for `parse_pathspec_file()`.
Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>