allow new restriction for JourneyPart #26

	# Block PRs targeting wip branches (v2.1-wip, v3.0-wip) when they are
	# behind their parent branch (v2.0 and v2.1-wip respectively).
	# This prevents unpropagated commits from accumulating, which leads to
	# costly backports of many commits generating large conflicts.
	# See https://github.com/TransmodelEcosystem/NeTEx/issues/982

	name: Check parent branch is up to date

	on:
	pull_request:
	branches: [v2.1-wip, v3.0-wip]

	jobs:
	parent-branch-is-up-to-date:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v4
	with:
	fetch-depth: 0

	- name: Verify base branch contains all parent commits
	run: \|
	case "${{ github.base_ref }}" in
	v2.1-wip) parent=v2.0 ;;
	v3.0-wip) parent=v2.1-wip ;;
	esac

	behind=$(git rev-list --count "origin/${{ github.base_ref }}..origin/$parent")
	if [ "$behind" -gt 0 ]; then
	echo "::error::${{ github.base_ref }} is $behind commit(s) behind $parent. Merge $parent into ${{ github.base_ref }} first."
	git log --oneline "origin/${{ github.base_ref }}..origin/$parent"
	exit 1
	fi

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