Add pre-commit for formatting, liniting and code checking.

[euronion]

Closes #242 .
Closes #239 .

Changes proposed in this Pull Request

Add checks, formatters and linters using pre-commit to the repository.
Especially includes:

• black formatting for Python
• formatting for yaml files
• REUSE check for FSFE REUSE compliance

Question:

• Should pre-commit be added to the environment.yaml? --> No
• Other hooks we should add?

TODOs:

• Update documentation: Add pre-commit encouragement (PR template + docu from atlite as template?)
• Remove pep8 recommendation from documentation
• Connect this repository with the (http://precommit.ci/) after merging this PR
• Add this PR after the next major release as an immediate minor release (mainly formattting) to keep change transparency for git blame

Checklist

• I tested my contribution locally and it seems to work fine.
• Code and workflow changes are sufficiently documented.
• Newly introduced dependencies are added to envs/environment.yaml and envs/environment.docs.yaml.
• [n/a] Changes in configuration options are added in all of config.default.yaml, config.tutorial.yaml, and test/config.test1.yaml.
• [n/a] Changes in configuration options are also documented in doc/configtables/*.csv and line references are adjusted in doc/configuration.rst and doc/tutorial.rst.
• A note for the release notes doc/release_notes.rst is amended in the format of previous release notes.

[FabianHofmann]

What I also use for linopy:

Isort sorts imports of packages

-   repo: https://github.com/PyCQA/isort
    rev: 5.9.3
    hooks:
      - id: isort
        args: ["--profile", "black", "--filter-files"]

codespell checks for spelling errors in comments and docstrings

-   repo: https://github.com/codespell-project/codespell
    rev: v2.1.0
    hooks:
    -   id: codespell
        types_or: [python, rst, markdown]
        files: ^(scripts|doc)/

[euronion]

Added. isort may be a bit controversial.

I had to exclude a regex for all CAPITAL CASE words for codespell, as it complained about the code strings THS and BA in scripts/build_shapes.py

[fneum]

Re question what to add: I like under pre-commit-hooks

  - id: check-added-large-files
    args: ['--maxkb=1000']

[euronion]

Re question what to add: I like under pre-commit-hooks

  - id: check-added-large-files
    args: ['--maxkb=1000']

Added, but with 2 MB as a limit. Our pictures in the documentations are sometimes larger than 1 MB.

[fneum]

Added, but with 2 MB as a limit. Our pictures in the documentations are sometimes larger than 1 MB.

Fair enough 🔢

[fneum]

This is now hot again @FabianHofmann @euronion.

[euronion]

Given that we already have a large number of commits in the master I suggest we postpone it (again) until a minor release.