add nightly updating workflow

Author: paulsohn

.github/workflows/update-nightly-submodules.yaml

@@ -0,0 +1,54 @@
+# Update submodules to nightly.
+# .repos sync is not handled here (maybe run pre-commit once?)
+name: Update Nightly Submodules
+
+on:
+  schedule:
+    - cron: '0 0 * * *'  # Every day at 00:00 UTC
+  workflow_dispatch:
+
+jobs:
+  update-nightly-submodules:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 1
+
+      - name: Generate token
+        id: generate-token
+        uses: tibdex/github-app-token@v2
+        with:
+          app_id: ${{ secrets.APP_ID }}
+          private_key: ${{ secrets.PRIVATE_KEY }}
+
+      - name: Set git config
+        uses: autowarefoundation/autoware-github-actions/set-git-config@v1
+        with:
+          token: ${{ steps.generate-token.outputs.token }}
+
+      - name: Update nightly submodules
+        id: update-nightly-submodules
+        env:
+          MAIN_BRANCH_NAME: main
+          NIGHTLY_BRANCH_NAME: nightly
+          GITHUB_TOKEN: ${{ steps.generate-token.outputs.token }}
+        run: |
+          git checkout "${MAIN_BRANCH_NAME}"
+          git checkout -B "${NIGHTLY_BRANCH_NAME}"
+
+          # Check if repository has submodules
+          if [ ! -f .gitmodules ]; then
+            echo "Error: The repository is not using git submodules"
+            exit 1
+          fi
+
+          git submodule update --init --checkout
+          git submodule update --remote
+          git add .
+          git commit -m "chore: update nightly submodules from ${MAIN_BRANCH_NAME}" || echo "No submodule updates to commit"
+          git push origin "${NIGHTLY_BRANCH_NAME}" --force-with-lease