dirstate: add/improve method docstrings.
- add doc to __init__(), _map(), status()
- enhance for __getitem__()
- fix inaccurate doc for walk() (described wrong return type)
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.