fast-forward-stable.yaml

name: Fast-forward stable branch from dev (Bodies of Water)

on:
  push:
    branches:
      - dev
  workflow_dispatch:
    inputs:
      dry_run:
        description: 'Run in dry-run mode (no actual push)'
        required: false
        default: false
        type: boolean

jobs:
  fast-forward:
    runs-on: ubuntu-latest
    permissions:
      contents: write

    steps:
      - name: Checkout repository
        uses: actions/checkout@v4
        with:
          fetch-depth: 0
          token: ${{ secrets.GITHUB_TOKEN }}

      - name: Configure Git
        run: |
          git config --global user.name "github-actions[bot]"
          git config --global user.email "github-actions[bot]@users.noreply.github.com"

      - name: Fetch all branches
        run: |
          git fetch origin dev
          git fetch origin stable

      - name: Check if dev and stable are the same
        id: check_changes
        run: |
          DEV_SHA=$(git rev-parse origin/dev)
          STABLE_SHA=$(git rev-parse origin/stable)

          echo "dev_sha=$DEV_SHA" >> $GITHUB_OUTPUT
          echo "stable_sha=$STABLE_SHA" >> $GITHUB_OUTPUT

          if [ "$DEV_SHA" = "$STABLE_SHA" ]; then
            echo "has_changes=false" >> $GITHUB_OUTPUT
            echo "✅ Dev and stable branches are already at the same commit ($DEV_SHA)"
          else
            echo "has_changes=true" >> $GITHUB_OUTPUT
            echo "📋 Dev is at: $DEV_SHA"
            echo "📋 Stable is at: $STABLE_SHA"
          fi

      - name: Check if fast-forward is possible
        id: check_ff
        if: steps.check_changes.outputs.has_changes == 'true'
        run: |
          # Create and switch to local stable branch tracking remote
          git checkout -b stable origin/stable

          # Check if we can fast-forward merge dev into stable
          if git merge-base --is-ancestor origin/stable origin/dev; then
            echo "can_fast_forward=true" >> $GITHUB_OUTPUT
            echo "✅ Fast-forward is possible - stable is an ancestor of dev"

            # Show what commits will be added
            echo "📋 Commits that will be fast-forwarded:"
            git log --oneline origin/stable..origin/dev
          else
            echo "can_fast_forward=false" >> $GITHUB_OUTPUT
            echo "❌ Fast-forward is not possible - stable has diverged from dev"

            # Show the divergence
            echo "📋 Commits in stable not in dev:"
            git log --oneline origin/dev..origin/stable
            echo "📋 Commits in dev not in stable:"
            git log --oneline origin/stable..origin/dev

            exit 1
          fi

      - name: Perform fast-forward merge
        id: fast_forward
        if: steps.check_changes.outputs.has_changes == 'true' && steps.check_ff.outputs.can_fast_forward == 'true'
        run: |
          # Ensure we're on stable branch
          git checkout stable

          # Perform the fast-forward merge
          git merge --ff-only origin/dev

          # Verify the merge was successful
          NEW_STABLE_SHA=$(git rev-parse stable)
          DEV_SHA="${{ steps.check_changes.outputs.dev_sha }}"

          if [ "$NEW_STABLE_SHA" = "$DEV_SHA" ]; then
            echo "merge_successful=true" >> $GITHUB_OUTPUT
            echo "new_stable_sha=$NEW_STABLE_SHA" >> $GITHUB_OUTPUT
            echo "✅ Fast-forward merge successful"
            echo "📋 Stable branch is now at: $NEW_STABLE_SHA"
          else
            echo "merge_successful=false" >> $GITHUB_OUTPUT
            echo "❌ Fast-forward merge failed - SHA mismatch"
            echo "Expected: $DEV_SHA"
            echo "Got: $NEW_STABLE_SHA"
            exit 1
          fi

      - name: Push changes (dry-run check)
        if: steps.check_changes.outputs.has_changes == 'true' && steps.fast_forward.outputs.merge_successful == 'true' && inputs.dry_run == true
        run: |
          echo "🔍 DRY RUN MODE - Would push the following changes:"
          echo "📋 Stable branch would be updated to: ${{ steps.fast_forward.outputs.new_stable_sha }}"
          echo "📋 This matches dev branch SHA: ${{ steps.check_changes.outputs.dev_sha }}"
          git log --oneline ${{ steps.check_changes.outputs.stable_sha }}..${{ steps.fast_forward.outputs.new_stable_sha }}

      - name: Push changes to stable
        if: steps.check_changes.outputs.has_changes == 'true' && steps.fast_forward.outputs.merge_successful == 'true' && inputs.dry_run != true
        run: |
          git push origin stable
          echo "✅ Successfully pushed fast-forward changes to stable branch"

      - name: Verify final state
        if: steps.check_changes.outputs.has_changes == 'true' && steps.fast_forward.outputs.merge_successful == 'true' && inputs.dry_run != true
        run: |
          # Fetch the latest state from remote
          git fetch origin stable

          # Verify remote stable matches what we expect
          REMOTE_STABLE_SHA=$(git rev-parse origin/stable)
          EXPECTED_SHA="${{ steps.check_changes.outputs.dev_sha }}"

          if [ "$REMOTE_STABLE_SHA" = "$EXPECTED_SHA" ]; then
            echo "✅ Verification successful!"
            echo "📋 Remote stable branch SHA: $REMOTE_STABLE_SHA"
            echo "📋 Dev branch SHA: $EXPECTED_SHA"
            echo "📋 Both branches are now synchronized"
          else
            echo "❌ Verification failed!"
            echo "📋 Remote stable SHA: $REMOTE_STABLE_SHA"
            echo "📋 Expected SHA: $EXPECTED_SHA"
            exit 1
          fi

      - name: Summary
        if: always()
        run: |
          echo "## Fast-forward Summary" >> $GITHUB_STEP_SUMMARY
          echo "" >> $GITHUB_STEP_SUMMARY

          if [ "${{ steps.check_changes.outputs.has_changes }}" = "false" ]; then
            echo "✅ **No changes needed** - dev and stable branches are already synchronized" >> $GITHUB_STEP_SUMMARY
            echo "- Both branches at commit: \`${{ steps.check_changes.outputs.dev_sha }}\`" >> $GITHUB_STEP_SUMMARY
          elif [ "${{ steps.check_ff.outputs.can_fast_forward }}" = "false" ]; then
            echo "❌ **Fast-forward failed** - stable branch has diverged from dev" >> $GITHUB_STEP_SUMMARY
            echo "- Manual intervention required to resolve branch divergence" >> $GITHUB_STEP_SUMMARY
          elif [ "${{ inputs.dry_run }}" = "true" ]; then
            echo "🔍 **Dry run completed successfully**" >> $GITHUB_STEP_SUMMARY
            echo "- Fast-forward is possible and would update stable to: \`${{ steps.fast_forward.outputs.new_stable_sha }}\`" >> $GITHUB_STEP_SUMMARY
          elif [ "${{ steps.fast_forward.outputs.merge_successful }}" = "true" ]; then
            echo "✅ **Fast-forward completed successfully**" >> $GITHUB_STEP_SUMMARY
            echo "- Stable branch updated to: \`${{ steps.fast_forward.outputs.new_stable_sha }}\`" >> $GITHUB_STEP_SUMMARY
            echo "- Both dev and stable branches are now synchronized" >> $GITHUB_STEP_SUMMARY
          else
            echo "❌ **Fast-forward failed**" >> $GITHUB_STEP_SUMMARY
            echo "- Check the workflow logs for detailed error information" >> $GITHUB_STEP_SUMMARY
          fi