Force extension for given file type in a hook

Question

How can I configure a pre-commit hook which will force yaml/yml files to have yaml extension. Pass:

lol.yaml

Fail:

lol.yml

Answer 1

Actually it turned out to be fairly easy. It's enough to add the following hook to the config:

  - repo: local
    hooks:
      - id: yaml-file-extension
        name: Check if YAML files has *.yaml extension.
        entry: YAML filenames must have .yaml extension.
        language: fail
        files: .yml$

It will not verify the content however, just the extension.