CI: Add workflow to enforce rebase before merge #13

	name: Force rebased

	on: [pull_request]

	jobs:
	force-rebase:
	runs-on: ubuntu-latest
	steps:
	- name: 'PR commits + 1'
	run: echo "PR_FETCH_DEPTH=$(( ${{ github.event.pull_request.commits }} + 1 ))" >> "${GITHUB_ENV}"

	- name: 'Checkout PR branch and all PR commits'
	uses: actions/checkout@v4
	with:
	ref: ${{ github.event.pull_request.head.sha }}
	fetch-depth: ${{ env.PR_FETCH_DEPTH }}

	- name: Show git log
	shell: bash
	run: \|
	git log

	- name: Check if branch is up-to-date
	shell: bash
	run: \|
	git merge-base --is-ancestor ${{ github.event.pull_request.base.sha }} HEAD

	- name: Check for merge commits
	shell: bash
	run: \|
	merges=$(git log --oneline HEAD~${{ github.event.pull_request.commits }}...HEAD --merges ); \
	echo "--- Merges ---\n${merges}"; \
	[ -z "${merges}" ]

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