mq: preserve --git flag when merging patches
Without this, merging a patch queue without diff.git=1 downgrades all git
patches to regular patches, losing data in the process.
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.