add only_changed input to run rubocop only against changed files #70

	name: CI
	on: [pull_request]
	jobs:
	test-skip-install-and-use-bundler:
	name: runner / rubocop
	runs-on: ubuntu-latest
	defaults:
	run:
	working-directory: test/using_bundler
	env:
	BUNDLE_GEMFILE: ${{ github.workspace }}/test/using_bundler/Gemfile
	steps:
	- uses: actions/checkout@v4
	- name: Fetch all commits for PR branch plus head commit of base branch
	run: \|
	# fetch all commits of the PR branch
	git fetch --shallow-exclude "${{ github.base_ref }}" origin "${{ github.ref }}"
	# fix for "fatal: error in object: unshallow"
	git repack -d
	# fetch head commit of base branch
	git fetch --deepen 1 origin "${{ github.ref }}"
	- uses: ruby/setup-ruby@v1
	with:
	ruby-version: 2.6
	bundler-cache: true
	- name: rubocop with skip install and using bundler
	uses: ./
	with:
	github_token: ${{ secrets.github_token }}
	skip_install: 'true'
	use_bundler: 'true'
	- run: test "$(bundle exec rubocop --version)" == "1.18.1"

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