Add bot to reformat code

[astrojuanlu]

When first-time contributors open a pull request, usually they are not aware that they have to run tox -e reformat before committing. Although we have documented these steps in our CONTRIBUTING.md (but not on our Contribute page!), it is normal that some people don't read it.

What usually happens next is that we have to either merge code with a failing quality check (we almost never do that) or ask the user to amend some silly whitespace issues (which is annoying and not always fool-proof).

Instead of fighting against this, I propose we have a bot that we can ask

@bot, please reformat code

and then it pushes another commit to the same branch.

Similar examples:

• @conda-forge-admin, used in conda-forge recipes. See https://conda-forge.org/docs/maintainer/infrastructure.html#admin-web-services, source code at https://github.com/conda-forge/conda-forge-webservices
• /run-recipe-test, used in pangeo recipes. See https://github.com/pangeo-forge/staged-recipes/blob/master/.github/workflows/run-recipe-test.yaml

[astrojuanlu]

What sorcery is this 😱 pradyunsg/furo@37bfcc4 Looks like https://pre-commit.ci/ is what we need?

[matthewfeickert]

Looks like https://pre-commit.ci/ is what we need?

I was going to say, pre-commit.ci is the way to go! :) We use it extensively in Scikit-HEP (c.f. developer recommendations) and the fact that it just takes care of things and pushes back is super nice.

Would you be open to a PR that simply implements

poliastro/tox.ini

Lines 64 to 72 in 2e38094

	[testenv:reformat]
	description = reformats the code using black and isort
	deps =
	black==21.5b0
	isort
	skip_install = true
	commands =
	isort --project poliastro --section-default THIRDPARTY src tests
	black src tests

in .pre-commit-config.yaml (this also requires poliastro to register for pre-commit.ci)?

[astrojuanlu]

Absolutely @matthewfeickert ! 🙌🏼