Trivial path optimization test

Trivial path optimization test

Linus:
    get_pathspec() does turn '.' into an empty string (which is
    correct - git internally does _not_ ever understand the notion of
    "." as the current working directory), but it doesn't ever do the
    optimization of noticing that a pathspec that consists solely of
    an empty string is "equivalent" to an empty pathspec.

The test is to ensure that this behaviour stays.

Signed-off-by: Alex Riesen <raa.lkml@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>