Add precommit configuration

[Zeitsperre]

Closes #46.

What does this introduce?

Pre-commit is a tool for running checks on code changes prior to committing them, preventing errors and inconsistencies from being introduced. I've added a pretty simple configuration that does a handful of things:

• Runs black and a subset of black-compatible flake8 checks over the code base
• Removes trailing whitespaces and adds an empty newline at the end of files
• Sorts import statements consistent with Black
• Checks for redundant # noqa statements

I've also added, but commented out, a few checks that require some effort.

• Check Manifest file for any missing/unaccounted files (requires manifest file made in Add a MANIFEST.in file, docs typo fixes #47.)
• PyDocStyle is a grammatical linter for writing consistent docstrings. Many changes needed. Willing to open more PRs for this.

[KipCrossing]

@Zeitsperre What's the best way to test this on my local?

Should we add a check for mypy too?

#47 has been approved, so feel free to merge

PyDocStyle sounds very opinionated, we should discuss the advantages in another PR.

[Zeitsperre]

@Zeitsperre What's the best way to test this on my local?

To configure pre-commit in the repo:

$ pip install pre-commit
$ pre-commit install

This will make it so that anytime you commit a file, the pre-commit linters and checkers will run automatically.

To run the checks manually:

$ pre-commit run --all-files

Should we add a check for mypy too?

We can! And will do!

#47 has been approved, so feel free to merge

Thanks!

PyDocStyle sounds very opinionated, we should discuss the advantages in another PR.

Sounds good to me. The documentation conventions/style can be different depending on preferences. I'm partial to numpy-docstyle conventions, but others are supported. Will open an issue concerning it.

[KipCrossing]

Should we add pre-commit as a dev requirement?

And perhaps some instructions on how to use it?

Maybe there's a way to initiate pre-commit install via the setup.py when a dev install is run. - OR would that be a bit intrusive and we should instead leave it as an option in the readme

[KipCrossing]

BTW, I've tested it and it looks like it will be a handy tool; especially to save some time when waiting for CI on GitHub just for it to fail (eg mypy).

[KipCrossing]

Feel free to merge - but at the very least we should mention the pre-commit option in the CONTRIBUTING doc

[Zeitsperre]

Hi @KipCrossing sorry for the delay!

In terms of time-saving, pre-commit is fantastic, and I've integrated it into many of the projects I help run. I can copy-paste some explanatory flavour text into the docs somewhere in this PR.

I like your idea of installing pre-commit when one makes a dev install. I know there's a way to do this. Can certainly look into it.

Edit: Looks like there's a suggestion in the docs https://pre-commit.com/#automatically-enabling-pre-commit-on-repositories

Edit 2: Some discussions within the pre-commit issues talk about how it would be a bit overarching to install pre-commit on clone/install. The better approach is to be clear in the dev docs about how to effectively contribute.