rebase: fix rebase with no common ancestors (
issue4446)
The new rebase revset didn't check for the case when there are no common
ancestors. Now it does. The new behavior should be the same as the pre-3.2
behavior. Added a test.
To run the tests, do:
cd tests/
python run-tests.py
See http://mercurial.selenic.com/wiki/WritingTests for
more information on writing tests.