label-pr.yml

name: Label PR
on:
  pull_request:
    types: [ opened, reopened, edited, synchronize ]

jobs:
  label_pr:
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write
    steps:
      - name: Calculate branch label
        id: branch-label
        run: |

          # Short name for current branch. For PRs, use target branch (base ref)
          # Reference: https://stackoverflow.com/questions/60300169/how-to-get-branch-name-on-github-action
          GIT_BRANCH=${GITHUB_BASE_REF:-${GITHUB_REF#refs/heads/}}
          echo "GIT_BRANCH=$GIT_BRANCH"

          LABEL=""
          if [[ $GIT_BRANCH = main ]]; then
            # Do not label main branch PRs
            LABEL="skip"
          elif [[ $GIT_BRANCH = main* ]]; then
            # Label release branches
            LABEL="branch-release"
          else
            # Label all other branches as invalid
            LABEL="branch-invalid"
          fi
          echo "label=$LABEL" >> $GITHUB_OUTPUT

      - uses: actions/github-script@v6
        if: steps.branch-label.outputs.label != 'skip'
        with:
          script: |
            github.rest.issues.addLabels({
              issue_number: context.issue.number,
              owner: context.repo.owner,
              repo: context.repo.repo,
              labels: ["${{steps.branch-label.outputs.label}}"]
            })