graft: warn when -r is combined with revisions as positional arguments
The behaviour in this case is undefined. Instead of silently doing something
"random" and surprising, at least issue a warning.
(This should perhaps be considered a "deprecation" and turned into an error in
a future release.)
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.