format: create new repository as 'generaldelta' by default
Since we have pushed back the performance issue related to general delta behind
another configuration (Still off by default), we can safely create new
repository with general delta support. As client are compatible with it since
Mercurial 1.9 (4.5 years ago) I do no expect any significant compatibility
issues.
To run the tests, do:
cd tests/
python run-tests.py
See https://mercurial-scm.org/wiki/WritingTests for
more information on writing tests.