Add a swift-format check to run on PRs. #1

	name: swift-format Check

	on:
	pull_request:
	branches: [ main ]

	jobs:
	format-check:
	name: swift-format Check
	runs-on: ubuntu-latest
	container:
	# Use use the latest Swift release and that's the version of swift-format
	# people should use.
	image: swift:latest
	steps:
	- name: Checkout
	uses: actions/checkout@v4
	- name: Mark the workspace as safe
	# https://github.com/actions/checkout/issues/766
	run: git config --global --add safe.directory ${GITHUB_WORKSPACE}
	- name: Run format check
	run: \|
	set -eu
	git ls-files -z '*.swift' \| xargs -0 swift format format --parallel --in-place
	GIT_PAGER='' git diff --exit-code '*.swift'
	- name: Run format lint check
	run: \|
	set -eu
	git ls-files -z '*.swift' \| xargs -0 swift format lint --strict --parallel

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