format.yml

name: Clang format

on: [pull_request]

jobs:
  clang-format:
    # We need at least 20.04 to install clang-format-11.
    runs-on: ubuntu-20.04
    steps:
      - uses: actions/checkout@v2
        with:
          ref: ${{ github.event.pull_request.head.sha }}
          # To get the merge base, we need the full history.
          fetch-depth: 0
      - name: Install prerequisites
        env:
          DEBIAN_FRONTEND: noninteractive
        run: |
          sudo apt update -y
          sudo apt install -y clang-format-11
          sudo update-alternatives --install /usr/bin/clang-format clang-format /usr/bin/clang-format-11 100
          sudo update-alternatives --install /usr/bin/git-clang-format git-clang-format /usr/bin/git-clang-format-11 100
      - name: Run clang-format on changed files
        run: |
          set -x
          git fetch origin ${{ github.event.pull_request.base.ref }}
          git fetch origin pull/${{ github.event.pull_request.number }}/head:${{ github.event.pull_request.head.ref }}
          BASE_COMMIT=$(git merge-base HEAD ${{ github.event.pull_request.base.sha }})
          COMMIT_FILES=$(git diff --diff-filter=d --name-only "$BASE_COMMIT" -- '*.cxx' '*.h' ':!*LinkDef*')
          if [ "$COMMIT_FILES" == "" ]; then
            exit 0 ;# nothing to check
          fi

          RESULT_OUTPUT=$(git-clang-format --commit ${BASE_COMMIT} --diff ${COMMIT_FILES})
          if [ "$RESULT_OUTPUT" == "no modified files to format" ] || [ "$RESULT_OUTPUT" == "clang-format did not modify any files" ]; then
            exit 0 ;# all good
          else
            git-clang-format --commit $BASE_COMMIT --diff
            echo "$RESULT_OUTPUT"
            exit 1
          fi