Add check for migrator filename uniqueness #4

	name: Check Migration Filename Uniqueness

	on:
	pull_request:
	types: [opened, synchronize, reopened]

	jobs:
	migration-check:
	runs-on: ubuntu-latest
	permissions:
	contents: read
	pull-requests: read

	steps:
	- name: Checkout code
	uses: actions/checkout@v4
	with:
	fetch-depth: 0 # fetch full history so we can diff properly

	- name: Fetch base branch
	run: \|
	git fetch origin ${{ github.base_ref }} --depth=1

	- name: Find newly added migration files
	id: find_files
	run: \|
	# Diff only added files between base branch and PR HEAD
	files=$(git diff --name-only --diff-filter=A origin/${{ github.base_ref }}...HEAD \| grep '^recipe/migrations/' \|\| true)

	echo "new_migrators=$new_migrators" >> $GITHUB_OUTPUT

	- name: Search for existing uses of that migrator in conda-forge
	if: steps.find_files.outputs.new_migrators != ''
	run: \|
	failed=0
	for m in ${new_migrators}; do
	migrator=$(basename "$m")
	echo "Checking for existing uses of migrator $migrator in conda-forge..."

	# Search in GH-org with exact path where migrators end up
	num_hits=$(gh search code "org:conda-forge path:.ci_support/migrations/$migrator" --json repository --jq 'map(select(.repository.isArchived == false)) \| length')

	if [ "$num_hits" -gt 0 ]; then
	echo "Found $num_hits existing occurrences of migrator $migrator in conda-forge"
	failed=1
	else
	echo "No existing occurrences of $migrator found"
	fi
	done

	if [ "$failed" -eq 1 ]; then
	echo "Pre-existing uses of migration filename(s) found in conda-forge."
	exit 1
	fi

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