Add clang-format check (AliceO2Group#4)

.github/workflows/code-formatting.yml

@@ -0,0 +1,98 @@
+name: Check PR with clang-format
+
+on: [pull_request_target]
+
+jobs:
+  build:
+    # 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 }}
+        persist-credentials: false
+        # We need the history of the dev branch all the way back to where the PR
+        # diverged. We're fetching everything here, as we don't know how many
+        # commits back that point is.
+        fetch-depth: 0
+
+    - name: Install prerequisites
+      env:
+        DEBIAN_FRONTEND: noninteractive
+      run: |
+        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
+      id: clang_format
+      env:
+        ALIBUILD_GITHUB_TOKEN: ${{secrets.ALIBUILD_GITHUB_TOKEN}}
+      run: |
+        set -x
+        # We need to fetch the other commit.
+        git fetch origin ${{ github.event.pull_request.base.ref }} \
+                         pull/${{ github.event.pull_request.number }}/head:${{ github.event.pull_request.head.ref }}
+
+        # We create a new branch which we will use for the eventual PR.
+        git config --global user.email "alibuild@cern.ch"
+        git config --global user.name "ALICE Action Bot"
+        git checkout -b alibot-cleanup-${{ github.event.pull_request.number }} ${{ github.event.pull_request.head.sha }}
+
+        # github.event.pull_request.base.sha is the latest commit on the branch
+        # the PR will be merged into, NOT the commit this PR derives from! For
+        # that, we need to find the latest common ancestor between the PR and
+        # the branch we are merging into.
+        BASE_COMMIT=$(git merge-base HEAD ${{ github.event.pull_request.base.sha }})
+        echo "Running clang-format against branch ${{ github.event.pull_request.base.ref }}, with hash ${{ github.event.pull_request.base.sha }}"
+        COMMIT_FILES=$(git diff --diff-filter d --name-only $BASE_COMMIT)
+        [ -n "$COMMIT_FILES" ] || { echo "No files to check" ; exit 0; }
+        RESULT_OUTPUT=$(git-clang-format --commit $BASE_COMMIT --diff --style file $COMMIT_FILES)
+
+        for x in $COMMIT_FILES; do
+          case $x in
+            *.hxx|*.cc|*.hpp) echo "$x uses non-allowed extension." && exit 1 ;;
+            *) ;;
+          esac
+        done
+
+        if [ "$RESULT_OUTPUT" = 'no modified files to format' ] ||
+           [ "$RESULT_OUTPUT" = 'clang-format did not modify any files' ]
+        then
+          echo "clang-format passed."
+          git push --set-upstream https://alibuild:$ALIBUILD_GITHUB_TOKEN@github.com/alibuild/O2Physics.git :alibot-cleanup-${{ github.event.pull_request.number }} -f || true
+          echo ::set-output name=clean::true
+        else
+          git-clang-format --diff --commit $BASE_COMMIT --style file $COMMIT_FILES |
+            patch -p1
+          echo "clang-format failed."
+          echo "To reproduce it locally please run"
+          echo -e "\tgit checkout ${{ github.event.pull_request.head.ref }}"
+          echo -e "\tgit-clang-format --commit $BASE_COMMIT --diff --style file"
+          echo "Note: using clang-format version $(clang-format --version)"
+          echo "Opening a PR to your branch with the fixes"
+          git commit -m 'Please consider the following formatting changes' -a
+          git show | cat
+          git fetch https://github.com/AliceO2Group/O2Physics.git pull/${{ github.event.pull_request.number }}/head
+          git push --set-upstream https://alibuild:$ALIBUILD_GITHUB_TOKEN@github.com/alibuild/O2Physics.git HEAD:refs/heads/alibot-cleanup-${{ github.event.pull_request.number }} -f
+          echo ::set-output name=clean::false
+        fi
+
+    - name: pull-request
+      uses: alisw/pull-request@master
+      with:
+        source_branch: 'alibuild:alibot-cleanup-${{ github.event.pull_request.number }}'
+        destination_branch: '${{ github.event.pull_request.head.label }}'
+        github_token: ${{ secrets.ALIBUILD_GITHUB_TOKEN }}
+        pr_title: "Please consider the following formatting changes to #${{ github.event.pull_request.number }}"
+        pr_body: |
+          This PR cannot be merged as is. You should either run clang-format yourself and update the pull request, or merge this PR in yours.
+          You can find AliceO2 coding conventions at http://github.com/AliceO2Group/CodingGuidelines.
+      continue-on-error: true # We do not create PRs if the branch is not there.
+
+    - name: Exit with error if the PR is not clean
+      run: |
+        case ${{ steps.clang_format.outputs.clean }} in
+          true) echo 'PR clean' ; exit 0 ;;
+          false) echo 'PR not clean' ; exit 1 ;;
+        esac