More refinements to rhub CI

.github/workflows/rhub.yaml

@@ -1,27 +1,33 @@
+# readxl-specific customization of ...
+
 # R-hub's generic GitHub Actions workflow file. It's canonical location is at
 # https://github.com/r-hub/actions/blob/v1/workflows/rhub.yaml
 # You can update this file to a newer version using the rhub2 package:
 #
 # rhub::rhub_setup()
 #
-# It is unlikely that you need to modify this file manually.
+# ~It is unlikely that you need to modify this file manually.~
 
-name: R-hub
+name: rhub.yaml
 run-name: "${{ github.event.inputs.id }}: ${{ github.event.inputs.name || format('Manually run by {0}', github.triggering_actor) }}"
 
 on:
+  push:
+    branches: [main, master]
+  pull_request:
   workflow_dispatch:
     inputs:
       config:
-        description: 'A comma separated list of R-hub platforms to use.'
+        description: 'A comma separated list of R-hub platforms to use. These default choices have been customized for readxl.'
         type: string
-        default: 'linux,windows,macos'
+        default: 'gcc-asan,valgrind,rchk,gcc15'
       name:
         description: 'Run name. You can leave this empty now.'
         type: string
       id:
         description: 'Unique ID. You can leave this empty now.'
         type: string
+permissions: read-all
 
 jobs:
 
@@ -36,6 +42,7 @@ jobs:
     - uses: r-hub/actions/setup@v1
       with:
         config: ${{ github.event.inputs.config }}
+        config: ${{ github.event.inputs.config ?? 'gcc-asan' }}
       id: rhub-setup
 
   linux-containers: