sync-main-to-dev.yml

name: 'Sync Branch Forward'

on:
  workflow_call:
    inputs:
      source-branch:
        description: 'Branch to sync from'
        required: false
        type: string
        default: 'main'
      target-branch:
        description: 'Branch to sync to'
        required: false
        type: string
        default: 'dev'
      create-pr-on-conflict:
        description: 'Open a PR if merge conflicts prevent automatic sync'
        required: false
        type: boolean
        default: true
      pr-labels:
        description: 'Comma-separated labels for conflict PRs'
        required: false
        type: string
        default: 'automated,sync'
      runs-on:
        description: 'Runner label to execute the job on'
        required: false
        type: string
        default: 'homelab-runners'
    secrets:
      token:
        description: 'GitHub token with repo write access (falls back to GITHUB_TOKEN)'
        required: false
    outputs:
      result:
        description: 'Sync result: fast-forward, merged, pr-created, up-to-date, or failed'
        value: ${{ jobs.sync.outputs.result }}
      pr-number:
        description: 'PR number if a conflict PR was created'
        value: ${{ jobs.sync.outputs.pr-number }}

permissions:
  contents: write
  pull-requests: write

jobs:
  sync:
    name: Sync ${{ inputs.source-branch }} to ${{ inputs.target-branch }}
    runs-on: ${{ inputs.runs-on }}
    timeout-minutes: 10
    outputs:
      result: ${{ steps.result.outputs.result }}
      pr-number: ${{ steps.conflict-pr.outputs.pr-number }}

    steps:
      - name: Checkout repository
        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
        with:
          fetch-depth: 0
          token: ${{ secrets.token || github.token }}

      - name: Configure git
        shell: bash
        run: |
          git config user.name "github-actions[bot]"
          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"

      - name: Check target branch exists
        id: check-target
        shell: bash
        run: |
          if git ls-remote --exit-code --heads origin "${{ inputs.target-branch }}" > /dev/null 2>&1; then
            echo "exists=true" >> "$GITHUB_OUTPUT"
          else
            echo "exists=false" >> "$GITHUB_OUTPUT"
            echo "::notice::Target branch '${{ inputs.target-branch }}' does not exist — it will be created from '${{ inputs.source-branch }}'."
          fi

      - name: Create target branch from source
        if: steps.check-target.outputs.exists == 'false'
        shell: bash
        run: |
          git checkout -b "${{ inputs.target-branch }}" "origin/${{ inputs.source-branch }}"
          git push origin "${{ inputs.target-branch }}"
          echo "::notice::Created '${{ inputs.target-branch }}' from '${{ inputs.source-branch }}'."

      - name: Compare branches
        if: steps.check-target.outputs.exists == 'true'
        id: compare
        shell: bash
        run: |
          BEHIND=$(git rev-list --count "origin/${{ inputs.target-branch }}..origin/${{ inputs.source-branch }}")
          AHEAD=$(git rev-list --count "origin/${{ inputs.source-branch }}..origin/${{ inputs.target-branch }}")
          echo "behind=$BEHIND" >> "$GITHUB_OUTPUT"
          echo "ahead=$AHEAD" >> "$GITHUB_OUTPUT"
          echo "Source is $BEHIND commit(s) ahead of target; target is $AHEAD commit(s) ahead of source."

      - name: Exit early if up-to-date
        if: steps.check-target.outputs.exists == 'true' && steps.compare.outputs.behind == '0'
        id: up-to-date
        shell: bash
        run: |
          echo "::notice::${{ inputs.target-branch }} is already up-to-date with ${{ inputs.source-branch }}."

      - name: Attempt fast-forward merge
        if: steps.check-target.outputs.exists == 'true' && steps.compare.outputs.behind != '0'
        id: fast-forward
        shell: bash
        run: |
          git checkout "${{ inputs.target-branch }}"
          if git merge --ff-only "origin/${{ inputs.source-branch }}"; then
            echo "success=true" >> "$GITHUB_OUTPUT"
          else
            echo "success=false" >> "$GITHUB_OUTPUT"
          fi

      - name: Attempt merge commit
        if: steps.fast-forward.outputs.success == 'false'
        id: merge-commit
        shell: bash
        run: |
          # Reset working tree from failed ff attempt
          git reset --hard "origin/${{ inputs.target-branch }}"
          if git merge --no-edit "origin/${{ inputs.source-branch }}"; then
            echo "success=true" >> "$GITHUB_OUTPUT"
          else
            echo "success=false" >> "$GITHUB_OUTPUT"
            git merge --abort
          fi

      - name: Push merged changes
        if: steps.fast-forward.outputs.success == 'true' || steps.merge-commit.outputs.success == 'true'
        shell: bash
        run: |
          git push origin "${{ inputs.target-branch }}"

      - name: Open conflict PR
        if: steps.merge-commit.outputs.success == 'false' && inputs.create-pr-on-conflict
        id: conflict-pr
        shell: bash
        env:
          GH_TOKEN: ${{ secrets.token || github.token }}
        run: |
          SYNC_BRANCH="sync/${{ inputs.source-branch }}-to-${{ inputs.target-branch }}"

          # Clean up stale sync branch if it exists
          git branch -D "$SYNC_BRANCH" 2>/dev/null || true
          git push origin --delete "$SYNC_BRANCH" 2>/dev/null || true

          # Create sync branch from source
          git checkout -b "$SYNC_BRANCH" "origin/${{ inputs.source-branch }}"
          git push origin "$SYNC_BRANCH"

          # Build label args as an array
          LABEL_ARGS=()
          IFS=',' read -ra LABELS <<< "${{ inputs.pr-labels }}"
          for label in "${LABELS[@]}"; do
            trimmed="${label## }"
            trimmed="${trimmed%% }"
            if [ -n "$trimmed" ]; then
              LABEL_ARGS+=(--label "$trimmed")
            fi
          done

          PR_BODY="## Automatic sync failed — merge conflicts detected

          This PR was created because \`${{ inputs.source-branch }}\` could not be automatically merged into \`${{ inputs.target-branch }}\`.

          **Please resolve the conflicts and merge this PR to complete the sync.**

          ---
          *Created by [sync-main-to-dev](https://github.com/samuelho-dev/git-flow) workflow*"
          # Strip leading whitespace added by YAML indentation
          PR_BODY="${PR_BODY//          /}"

          PR_URL=$(gh pr create \
            --base "${{ inputs.target-branch }}" \
            --head "$SYNC_BRANCH" \
            --title "sync: merge ${{ inputs.source-branch }} into ${{ inputs.target-branch }}" \
            --body "$PR_BODY" \
            "${LABEL_ARGS[@]}" 2>&1) || true

          PR_NUMBER=$(echo "$PR_URL" | grep -oP '/pull/\K\d+' || echo "")
          echo "pr-number=$PR_NUMBER" >> "$GITHUB_OUTPUT"
          echo "pr-url=$PR_URL" >> "$GITHUB_OUTPUT"

          if [ -n "$PR_NUMBER" ]; then
            echo "::notice::Opened conflict PR #$PR_NUMBER: $PR_URL"
          else
            echo "::warning::Failed to create conflict PR. Output: $PR_URL"
          fi

      - name: Determine result
        id: result
        if: always()
        shell: bash
        run: |
          if [ "${{ steps.check-target.outputs.exists }}" = "false" ]; then
            echo "result=fast-forward" >> "$GITHUB_OUTPUT"
          elif [ "${{ steps.compare.outputs.behind }}" = "0" ]; then
            echo "result=up-to-date" >> "$GITHUB_OUTPUT"
          elif [ "${{ steps.fast-forward.outputs.success }}" = "true" ]; then
            echo "result=fast-forward" >> "$GITHUB_OUTPUT"
          elif [ "${{ steps.merge-commit.outputs.success }}" = "true" ]; then
            echo "result=merged" >> "$GITHUB_OUTPUT"
          elif [ -n "${{ steps.conflict-pr.outputs.pr-number }}" ]; then
            echo "result=pr-created" >> "$GITHUB_OUTPUT"
          else
            echo "result=failed" >> "$GITHUB_OUTPUT"
          fi

      - name: Generate step summary
        if: always()
        shell: bash
        run: |
          RESULT="${{ steps.result.outputs.result }}"
          {
            echo "## Sync ${{ inputs.source-branch }} → ${{ inputs.target-branch }}"
            echo ""
          } >> "$GITHUB_STEP_SUMMARY"

          case "$RESULT" in
            up-to-date)
              echo "**Result:** Already up-to-date" >> "$GITHUB_STEP_SUMMARY"
              ;;
            fast-forward)
              echo "**Result:** Fast-forward merge" >> "$GITHUB_STEP_SUMMARY"
              ;;
            merged)
              echo "**Result:** Merge commit created" >> "$GITHUB_STEP_SUMMARY"
              ;;
            pr-created)
              {
                echo "**Result:** Conflict PR created"
                echo ""
                echo "**PR:** #${{ steps.conflict-pr.outputs.pr-number }}"
              } >> "$GITHUB_STEP_SUMMARY"
              ;;
            failed)
              echo "**Result:** Sync failed" >> "$GITHUB_STEP_SUMMARY"
              ;;
          esac

          if [ "${{ steps.compare.outputs.behind }}" != "" ] && [ "${{ steps.compare.outputs.behind }}" != "0" ]; then
            {
              echo ""
              echo "| Metric | Value |"
              echo "|--------|-------|"
              echo "| Commits to sync | ${{ steps.compare.outputs.behind }} |"
              echo "| Target ahead by | ${{ steps.compare.outputs.ahead }} |"
            } >> "$GITHUB_STEP_SUMMARY"
          fi