Further optimizations and tweaks to the new GH action

Signed-off-by: Bernd Finger <bfinger@redhat.com>

Author: berndfinger

.github/workflows/pr-branch-check.yml

@@ -1,20 +1,25 @@
-name: Check source branch
+name: Check PR branches
 
 on:
   pull_request:
     branches:
       - main
+      - dev
     types:
       - opened
       - synchronize
       - reopened
+      # Ensure re-check when branch is switched after PR is opened:
+      - edited
 
 jobs:
-  check-source-branch:
+  check-pr-branches:
     runs-on: ubuntu-latest
+    # Only run if it is not an edit OR if it is an edit to the base branch:
+    if: github.event.action != 'edited' || github.event.changes.base.ref.from != null
     steps:
-      - name: Check if PR is from dev branch
-        if: github.head_ref != 'dev'
+      - name: Check if PR to main is from dev branch
+        if: github.base_ref == 'main' && github.head_ref != 'dev'
         run: |
           echo "PRs to the main branch are only allowed from the dev branch!"
           exit 1