If you don't have a "--" marker, then:
- all of the arguments we are going to assume are pathspecs
must exist in the working tree.
- none of the arguments we parsed as revisions could be
interpreted as a filename.
so that there really isn't any possibility of confusion in case
somebody does have a revision that looks like a pathname too.
The former rule has been in effect; this implements the latter.
Signed-off-by: Junio C Hamano <junkio@cox.net>