t1430: add another refs-escape test

In t1430, we check whether deleting the branch "../../foo" will delete ".git/foo". However, this is not that interesting a test; the precious file ".git/foo" does not look like a ref, so even if we did not notice the "escape" from the "refs/" hierarchy, we would fail for that reason (i.e., if you turned refname_is_safe into a noop, the test still passes). Let's add an additional test for the same thing, but with a file that actually looks like a ref. That will make sure we are exercising the refname_is_safe code. While we're at it, let's also make the code work a little harder by adding some extra paths and some empty path components. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>