When "git push" is run without any refspec (neither on the
command line nor in the config), we used to push "matching refs"
in the sense that anything under refs/ hierarchy that exist on
both ends were updated.  This used to be a sane default for
publishing your repository to another back when we did not have
refs/remotes/ hierarchy, but it does not make much sense these
days.

This changes the semantics to push only "matching branches".
Signed-off-by: NJunio C Hamano <gitster@pobox.com>