directory rename detection: miscellaneous testcases to complete coverage

directory rename detection: miscellaneous testcases to complete coverage

I came up with the testcases in the first eight sections before coding up
the implementation.  The testcases in this section were mostly ones I
thought of while coding/debugging, and which I was too lazy to insert
into the previous sections because I didn't want to re-label with all the
testcase references.  :-)

Reviewed-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>