tests: run check-code.py on working directory files
If we insist on Mercurial sources to pass check-code.py, let automate the
process and make it part of the tests.
Objections?
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.