Run tests relying only on git fixtures

.github/workflows/tests.yml

@@ -34,6 +34,4 @@ jobs:
  python -m pip install -r requirements.txt
  python setup.py install
  - name: Run tests for ${{ matrix.python-version }}
- run: |
- git branch -m main # still master by default in GitHub Actions
- pytest -vvv
+ run: pytest -vvv