mq-safety: don't apply safety on non-outgoing changeset
When mq changeset are secret, they don't appear in outgoing and won't be
pushed. So it's not necessary to abort the push.
The checkpush call is protected by lock to prevent race on phase.
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
for software developers.
Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
See http://mercurial.selenic.com/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.