Log Message:
py-pygit2: updated to 1.4.0

1.4.0
- Upgrade to libgit2 1.1, new ``GIT_BLAME_IGNORE_WHITESPACE`` constant
- Add wheels for Python 3.9
- Drop support for PyPy3 7.2
- New optional ``flags`` argument in ``Repository.__init__(...)``,
  new ``GIT_REPOSITORY_OPEN_*`` constants
- Documentation