localrepository.status: only acquire wlock if actually needed.
This speeds up the common case of not needing to update the dirstate,
and avoids the need to reload and parse the dirstate "just in case".
Basic install:
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
See http://www.selenic.com/mercurial/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.