A Github action to clean out branches that have been merged into develop.

cleanup-branches.yml

# This task cleans out all branches that have been merged into develop, leaving
# stage and main alone. It compares by commit ID, so branches that have been
# squash merged or combined using some other way that alters commit IDs will not
# be detected as having been merged.
name: Cleanup Branches

on:
  workflow_dispatch:
    inputs:
      dry_run:
        description: 'Run in dry-run mode (preview changes without deleting)'
        required: false
        default: 'true'
        type: choice
        options:
          - 'true'
          - 'false'

jobs:
  cleanup:
    runs-on: ubuntu-latest
    container: python:2.7-alpine
    permissions:
      contents: write
    steps:
      - name: Install git
        run: |
          apk add --no-cache git

      # Cloning the repository using git command using GITHUB_TOKEN generated
      # for this action invocation so that we know the repository looks valid to
      # git-sweep. git-sweep does not work right if we use the checkout action.
      - name: Clone repository
        run: |
          git clone https://oauth2:${{ secrets.GITHUB_TOKEN }}@github.com/${{ github.repository }}.git .

      - name: Install git-sweep
        run: |
          pip install git-sweep

      - name: Run git-sweep cleanup
        run: |
          if [ "${{ github.event.inputs.dry_run }}" == "true" ]; then
            echo "Running in dry-run mode..."
            git-sweep preview --master develop --skip main,stage
          else
            echo "Running cleanup..."
            git-sweep cleanup --force --master develop --skip main,stage
          fi

      - name: Show results
        run: |
          echo "Current branches:"
          git branch -r