fix bug in prepush logic involving merge changesets When creating new branches and merging them into existing ones, you would sometimes be able to push some changesets (the existing branches) without using --force, even when that creates a new head on the remote. A test which triggers the error has been added.

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.