[feat] add trunk fmt pre-push hook

[Ryang20718]

A user may have multiple commits they want to add in series. whilst trunk fmt is fast, it may not be instantaneous. would be nice to have an option to run prepush

[trunk-io]

⏱️ 4m total CI duration on this PR

Job	Cumulative Duration	Recent Runs
CodeQL-Build	2m	🟩
Trunk Check runner [linux]	1m	🟩
Repo Tests / Plugin Tests	38s	🟩
Action Tests	19s	🟩
Detect changed files	8s	🟩
Aggregate Test Results	1s	🟩

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[TylerJang27]

Hi @Ryang20718, thanks for the PR! I think that this action will not work as intended, however. GIT_INDEX_FILE is something that comes from git as an input to a pre-commit hook. trunk-fmt-pre-commit uses that to modify the index in place, so that the correct formatting of your files gets committed (and you don't have to run git commit again).

For a pre-push hook, there's no such construct. If you still want to add something like this, you could do the following with a wrapper:

1. Check that the git workspace is clean
2. Run trunk fmt (probably just with --trigger=pre-push)
3. Add the changed files and commit them
4. Verify that the correct ref is still being pushed

Let me know what you think, it's possible that there's also another option to smooth out your workflow; what formatter is usually the slowest to complete?

[Ryang20718]

@TylerJang27 ready for a re-review!

[TylerJang27]

Can you add a comment explaining this action, since it's a slight departure from idiomatic usage?

[TylerJang27]

Suggested change

	- id: trunk-fmt-pre-push
	# We recommend using trunk-fmt-pre-commit in most cases, since it is
	# generally pretty fast and modifies the index. When running this action
	# via pre-push, note that it only reports unformatted files and doesn't modify
	# them or modify the index. You may wish to use this action if you have a
	# setup where formatters are too slow for pre-commit.
	- id: trunk-fmt-pre-push