ci: fix maintenance

.github/workflows/maintenance.yml

@@ -1,4 +1,4 @@
-name: Scripted maintenance
+name: maintenance
 
 on: [push, pull_request_target]
 
@@ -10,6 +10,8 @@ jobs:
       - uses: actions/checkout@v2
         with:
           ref: ${{ github.head_ref }}
+          repository: ${{ github.event.pull_request.head.repo.full_name }}
+          fetch-depth: 2
 
       - uses: actions/setup-python@v2
         with: