largefiles: test reverting largefiles (coverage creeping ever upwards)
This reveals a small bug: revert reports "reverting .hglf/largefile"
when it really should report "reverting largefile". I don't see an
easy fix, though (short of using ui.pushbuffer() to interfere with
revert's output).
To run the tests, do:
cd tests/
python run-tests.py
See http://mercurial.selenic.com/wiki/WritingTests for
more information on writing tests.