[Apply lint] Add PR-only pre-commit workflow & lint all #10

	name: pre-commit (PR only on changed files)

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

	jobs:
	detect_changes:
	runs-on: ubuntu-latest
	outputs:
	changed: ${{ steps.changed_files.outputs.changed }}

	steps:
	- name: Checkout full history
	uses: actions/checkout@v4
	with:
	fetch-depth: 0

	- name: Detect changed files
	id: changed_files
	run: \|
	git fetch origin ${{ github.base_ref }}
	CHANGED_FILES=$(git diff --name-only origin/${{ github.base_ref }}...HEAD)

	{
	echo "changed<<EOF"
	echo "$CHANGED_FILES"
	echo "EOF"
	} >> "$GITHUB_OUTPUT"

	- name: Show changed files
	run: \|
	echo "Changed files:"
	echo "${{ steps.changed_files.outputs.changed }}"

	precommit:
	needs: detect_changes
	runs-on: ubuntu-latest
	if: ${{ needs.detect_changes.outputs.changed != '' }}

	steps:
	- name: Checkout PR branch
	uses: actions/checkout@v4
	with:
	fetch-depth: 0
	ref: ${{ github.head_ref }}

	- name: Set up Python
	uses: actions/setup-python@v5
	with:
	python-version: "3.12"

	- name: Install pre-commit
	run: pip install pre-commit

	- name: Run pre-commit (CI check-only stage) on changed files
	env:
	CHANGED_FILES: ${{ needs.detect_changes.outputs.changed }}
	run: \|
	mapfile -t files <<< "$CHANGED_FILES"
	pre-commit run --hook-stage manual --files "${files[@]}" --show-diff-on-failure

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