feat: use PR instead of date

.gitea/workflows/render-manifests.yaml

@@ -111,6 +111,7 @@ jobs:
       - name: Prepare Manifest Branch
         id: prepare-manifest-branch
         env:
+          PR_NUMBER: ${{ github.event.pull_request.number }}
           IS_AUTOMERGE: ${{ steps.mode.outputs.is-automerge }}
         run: |
           cd "${MANIFEST_DIR}"
@@ -120,10 +121,10 @@ jobs:
           git config user.email "gitea-bot@alexlebens.net"
 
           if [[ "$IS_AUTOMERGE" == "true" ]]; then
+            BRANCH_NAME="${BRANCH_NAME_BASE}-automerge-${PR_NUMBER}"
             echo ""
             echo ">> Creating branch ${BRANCH_NAME} ..."
-            BRANCH_NAME="${BRANCH_NAME_BASE}-automerge-$(date +%Y%m%d%H%M%S)"
-            git checkout -b "$BRANCH_NAME"
+            git checkout -B "$BRANCH_NAME"
 
           else
             echo ""