commit: write last-message.txt with no content modifications.
This assumes the user will use either a sane editor (anything but
Notepad) or the same editor again: even Notepad should be able to read
what it previously wrote.
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.