format.yml

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@v6
        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@v6
        with:
          fetch-depth: 0
          ref: ${{ github.head_ref }}

      - name: Set up Python
        uses: actions/setup-python@v6
        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