[PATCH] allow pathspec to end with a slash

The recent rewrite broke "git-whatchanged -v -p drivers/usb/" but
"git-whatchanged -v -p drivers/usb" still works.  Just strip out the
trailing slashes internally to make it work again.

It uses compare-thing-with-number comparison order instead of visual
comparison order ;-).

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>