Rip out merge-order and make "git log <paths>..." work again.

Rip out merge-order and make "git log <paths>..." work again.

Well, assuming breaking --merge-order is fine, here's a patch (on top of
the other ones) that makes

	git log <filename>

actually work, as far as I can tell.

I didn't add the logic for --before/--after flags, but that should be
pretty trivial, and is independent of this anyway.

Signed-off-by: Junio C Hamano <junkio@cox.net>