Tests can be run with
```
bazel test //swift/codegen:tests
```
Coverage can be checked installing `pytest-cov` and running
```
pytest --cov=swift/codegen swift/codegen/test
```
This enables use of the `pre-commit` framework to run quick pre-commit
checks. In particular this allows to automatically fix:
* trailing white spaces
* absence or multiple newlines at the end of files
* QL code formatting
* file sync
More could be added in the future: anything that can be checked fast
can be added in the configuration (for example well-formedness of
`qldoc` files).
This is a purely opt-in feature. Instructions for enabling it and
possibly configuring its behaviour are in `pre-commit-hook-setup.md`.
