Migrate to lefthook from lint-staged + husky

[caugner]

Summary

Migrates to lefthook, replacing lint-staged and husky.

Also adds pre-push and post-merge hooks:

• The post-merge hook, limited to the main branch, runs npm install.
• The pre-push hook runs npm install, followed by lint commands (ESLint, prettier, tsc).

Test results and supporting details

Related issues

[ddbeck]

Does lefthook have something like Husky's HUSKY=0 envvar, to opt out of this? I rather dislike pre-commit hooks and don't wish to run them, if you apply this change (they're quite slow and disruptive, as somebody who commits a LOT, making heavy use of fixup and rebase).

[queengooborg]

Git itself has a way to disable hooks when committing -- --no-verify

[ddbeck]

OK, it turns out there is an environment variable option LEFTHOOK=0—I don't know why I couldn't find it last night—so I'm +0 on this PR.

@queengooborg it's not a good alternative. Setting aside having to remember to set --no-verify, other tools won't necessarily pass such an option through to git-commit.

[caugner]

I rather dislike pre-commit hooks and don't wish to run them, if you apply this change (they're quite slow and disruptive, as somebody who commits a LOT, making heavy use of fixup and rebase).

As someone who commits a lot too, I understand your concern about hooks very well.

I have now tweaked the pre-push and post-merge hook:

1. The pre-commit hook with lefthook now takes 1.02 seconds for me (M1 Macbook) on your draft PR, versus 2.94s with lint-staged.
2. The pre-push hook (without npm run lint) now takes 3.18s for me.
3. The post-merge hook (without npm run build) now takes 3.12s for me.

I would like to argue that these hooks are no longer slow and disruptive, and avoid you from running npm run lint:fix (on all files) manually.

@ddbeck Are these runtimes sufficiently low for you to reconsider keeping these hooks enabled in your BCD checkout?

[ddbeck]

@caugner ah yeah, that's really promising. I'm willing to give these a try. 👍

(also thank you for the nudge on the other PR—I completely forgot about it)

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.

[caugner]

@queengooborg Are you okay with merging this?

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.

[caugner]

If nobody objects, I will merge this on Monday.

[github-actions]

This pull request has merge conflicts that must be resolved before it can be merged.