Log Message:
py-pygit2: updated to 1.2.0

1.2.0:
- Drop support for Python 3.5
- Upgrade to libgit2 1.0
- New support for custom reference database backends
- New support for path objects
- New ``index`` optional parameter in ``Repository.checkout_index``
- New MacOS wheels
- Fix re-raise exception from credentials callback in clone_repository
- Fix warning with ``pip install pygit2``
- Tests: disable global Git config