Git 1.8.4-rc4

As we had to revert two topics at the last minute, let's have
another (hopefully short) round of rc to make sure the final release
will be sound.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Sync with v1.8.4-rc4

* master:
  Git 1.8.4-rc4