Add script to merge main into all active feature branches on a regular schedule.

.github/workflows/update-feature-branches.yml

@@ -2,11 +2,126 @@ name: Update Feature Branches
 on:
   workflow_dispatch:
     inputs:
+      branch_patterns:
+        description: 'Space-separated list of feature branch patterns'
+        default: 'feature_branch/*'
+        required: true
+      main_branch:
+        description: 'Main branch to merge'
+        default: 'main'
+        required: true
+  schedule:
+    - cron: "0 16 * * 1"  # Mondays, 4pm UTC = 9am PST / 10am PDT
+
+env:
+  defaultBranchPattern: "feature_branch/*"
+  defaultMainBranch: "main"
+  triggerTestsLabel: "tests-requested: quick"
 
 jobs:
-  no_op:
-    name: no-op
+  list_feature_branches:
+    name: list-feature-branches
+    runs-on: ubuntu-20.04
+    outputs:
+      branch_list: ${{ steps.get-branches.outputs.branch_list }}
+    steps:
+      - name: Check out repo (if needed)
+        if: ${{ github.event.inputs.branch_list == '' }}
+        uses: actions/checkout@v3
+
+      - name: Get list of feature branches
+        id: get-branches
+        run: |
+            branch_pattern='origin/${{ env.defaultBranchPattern }}'
+            if [[ -n '${{ github.event.inputs.branch_patterns }}' ]]; then
+              branch_pattern=origin/$(echo '${{ github.event.inputs.branch_patterns }}' | sed 's| | origin/|g')
+            fi
+            git remote update
+            echo "Branch pattern: ${branch_pattern}"
+            branch_list=$(git branch --list --all "${branch_pattern}")
+            if [[ -n ${branch_list} ]]; then
+              # If there's at least one entry, process the list.
+              echo "Remote branch list: ${branch_list}"
+              # Remove remotes/origin/ from each branch.
+              branch_list=$(echo ${branch_list} | sed 's| remotes/origin/| |g' | sed 's|^remotes/origin/||')
+              # Change spaces to commas.
+              branch_list=$(echo ${branch_list} | sed 's/ /,/g')
+              # Add quotes around each branch name.
+              branch_list='"'$(echo ${branch_list} | sed 's/,/","/g')'"'
+            fi
+            echo "::warning ::Branch list: [${branch_list}]"
+            echo "branch_list=[${branch_list}]" >> $GITHUB_OUTPUT
+
+  create_merge_prs:
+    name: create-merge-pr-${{ matrix.branch_name }}
+    needs: [ list_feature_branches ]
     runs-on: ubuntu-20.04
+    if: ${{ needs.list_feature_branches.outputs.branch_list != '[]' }}
+    strategy:
+      fail-fast: false
+      matrix:
+        branch_name: ${{ fromJson(needs.list_feature_branches.outputs.branch_list) }}
     steps:
-      - name: noop
-        run: true
+      - name: Get token for firebase-workflow-trigger
+        uses: tibdex/github-app-token@v1
+        id: generate-token
+        with:
+          app_id: ${{ secrets.WORKFLOW_TRIGGER_APP_ID }}
+          private_key: ${{ secrets.WORKFLOW_TRIGGER_APP_PRIVATE_KEY }}
+
+      - name: Setup python
+        uses: actions/setup-python@v4
+        with:
+          python-version: 3.7
+
+      - uses: actions/checkout@v3
+        with:
+          ref: ${{ matrix.branch_name }}
+          fetch-depth: 0
+          submodules: false
+
+      - name: Install prerequisites
+        run: |
+          python scripts/gha/install_prereqs_desktop.py
+          python -m pip install requests
+
+      - name: Create merge PR
+        id: create-pr
+        run: |
+            git config user.email "[email protected]"
+            git config user.name "firebase-workflow-trigger-bot"
+            git config core.commentChar "%"  # so we can use # in git commit messages
+
+            main_branch='${{ env.defaultMainBranch }}'
+            if [[ -n '${{ github.event.inputs.main_branch }}' ]]; then
+              main_branch='${{ github.event.inputs.main_branch }}'
+            fi
+            # Attempt a merge, then check if any files changed.
+            git merge --no-commit --no-ff "origin/${main_branch}" || true
+            if git diff --quiet ${{ matrix.branch_name }}; then
+              # No merge necessary.
+              echo "::warning ::No merge needed for ${{ matrix.branch_name }}, won't create pull request."
+              echo "created_pr_number=0" >> $GITHUB_OUTPUT
+              exit 0
+            fi
+
+            # Undo the actual merge. Let the PR creation handle it.
+            git merge --abort
+
+            date_str=$(date "+%b %d, %Y")
+
+            pr_title="Automatic merge of ${main_branch} into ${{ matrix.branch_name }} - ${date_str}"
+            pr_body="Automatic merge of ${main_branch} into ${{ matrix.branch_name }}.
+
+            > Created on ${date_str} by [${{github.workflow}} workflow]($GITHUB_SERVER_URL/$GITHUB_REPOSITORY/actions/runs/$GITHUB_RUN_ID).
+            "
+            pr_number=$(python scripts/gha/create_pull_request.py --token ${{ steps.generate-token.outputs.token }} --base "${{ matrix.branch_name }}" --head "${main_branch}" --title "${pr_title}" --body "${pr_body}")
+            echo "created_pr_number=${pr_number}" >> $GITHUB_OUTPUT
+
+      - name: Set test trigger label.
+        uses: actions-ecosystem/action-add-labels@v1
+        if: ${{ steps.create-pr.outputs.created_pr_number }}
+        with:
+          github_token: ${{ steps.generate-token.outputs.token }}
+          number: ${{ steps.create-pr.outputs.created_pr_number }}
+          labels: "${{ env.triggerTestsLabel }}"