This makes git-applymbox verify that the index matches the current HEAD
before it starts applying patches.

Otherwise, you might have updated the index with unrelated changes, and
the first patch will commit not just the patch from the mbox, but also any
changes you had in your index.
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>