Support pre-commit to run arbitrary entrypoints even if they don't have native pre-commit support

[Spitfire1900]

• I have added an entry to docs/changelog.md

Summary of changes

Add support for using pipx as a pre-commit hook for arbitrary python packages that do not have a pre-commit hook configured.
Some package utilities I'd like to use even but they don't have a pre-commit hook configured for them.

This allows configuration like the following to be added to a project .pre-commit-config.yaml file to run the script.

- repo: https://github.com/Spitfire1900/pipx
  rev: 9e59f26
  hooks:
  - id: pipx
    alias: yapf
    name: yapf
    args: ['yapf', '-i']
    types: ['python']

With the previous config the following command runs yapf against pipx's get-pipx.py as an example:

pre-commit run pipx --files .\get-pipx.py

Test plan

Tested by running the configuration from "Summary of changes" against my local pipx repo.

[uranusjr]

Since you basically should not use anything but pipx run, is it possible to include run in the default args so the user can (only) do args: ['yapf', '-i']?

Also it would be a good idea to add a link to pre-commit documentation in the section describing this.

[Spitfire1900]

@uranusjr; I initially tried this with args: ['run'] in .pre-commit-hooks.yaml, however testing showed that args in the local .pre-commit-config.yaml overrode instead of appending to args from .pre-commit-hooks.yaml.

[Spitfire1900]

I've updated the README to reference installation.doc for the pre-commit code snippet.

[dukecat0]

Suggested change

	rev: 1.3.0
	rev: 1.2.0

[Spitfire1900]

Pre-commit performs a git checkout against rev: and then looks for the .pre-commit-hooks.yaml file in the worktree; rev: 1.2.0 won't work as the file will be missing.

It looks like PRs are merged in pipx using the "squash" strategy, docs/installation.md will need to be updated post merge to update rev: to a valid commit hash.

[uranusjr]

I’m still very inclined to make this only possible to run pipx run and eliminate the run in the user command. Is it possible to get some advices from pre-commit maintainers on this?

[Spitfire1900]

I’m still very inclined to make this only possible to run pipx run and eliminate the run in the user command. Is it possible to get some advices from pre-commit maintainers on this?

I've successfully tested using entry: pipx run in ./.pre-commit-hooks.yaml; updated PR and docs

https://pre-commit.com/#hooks-entry

[uranusjr]

Should be ready when CI passes.

[chrysle]

All's passed!