ci: add Automerge and convert sphinx-tuttest to a reusable workflow

Signed-off-by: Unai Martinez-Corral <umartinezcorral@antmicro.com>

.github/workflows/Automerge.yml

@@ -0,0 +1,29 @@
+name: Automerge
+
+on:
+  pull_request:
+  push:
+  schedule:
+    - cron: '0 0 * * *'
+  workflow_dispatch:
+
+jobs:
+
+
+  Pipeline:
+    if: ${{ !(github.event_name != 'pull_request' && github.actor == 'dependabot[bot]') }}
+    uses: ./.github/workflows/sphinx-tuttest.yml
+
+
+  Automerge:
+    needs: Pipeline
+    if: github.event_name == 'pull_request' && github.actor == 'dependabot[bot]'
+    runs-on: ubuntu-latest
+    name: Automerge dependabot PRs
+    permissions:
+      contents: write
+
+    steps:
+
+      - name: Auto-merge Dependabot PR
+        run: GITHUB_TOKEN='${{ github.token }}' gh pr merge '${{ github.event.pull_request.html_url }}' --squash

.github/workflows/sphinx-tuttest.yml

@@ -1,10 +1,7 @@
 name: doc-test
 
 on:
- push:
+  workflow_call:
- pull_request:
- schedule:
-  - cron: "0 0 * * *"
 
 jobs: