t3401: add another directory rename testcase for rebase and am

t3401: add another directory rename testcase for rebase and am

Similar to commit 16346883ab ("t3401: add directory rename testcases for
rebase and am", 2018-06-27), add another testcase for directory rename
detection.  This new testcase differs in that it showcases a situation
where no directory rename was performed, but which some backends
incorrectly detect.

As with the other testcase, run this in conjunction with each of the
types of rebases:
  git-rebase--interactive
  git-rebase--am
  git-rebase--merge
and also use the same testcase for
  git am --3way

Reported-by: Nikolay Kasyanov <corrmage@gmail.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>