Run the mypy pre-commit only on staged files

[julienperichon]

By default, pre-commit gives only the staged files to each pre-commit command.

However, in Sicarator, we do the following:

  - id: type-check
    name: Type checking (mypy)
    entry: make type-check
    pass_filenames: false
    language: system
    types: [python]
    stages: [commit]

with make type-check as

type-check:
	poetry run mypy src

We could do something like this to run mypy only on staged files:

  - id: type-check
    name: Type checking (mypy)
    entry: mypy
    language: system
    types: [python]
    stages: [commit]

@ywolff What do you think ?

[ywolff]

Current behavior is on purpose, because you can break typing of a file foo.py while modifying only another file bar.py, if foo.py imports bar.py (which is not the case for linting or formatting, which are independent between files).
I agree that it can be a bit surprising and should be documented (in the pre-commit config), so I keep the issue open with a "Documentation" label.