run the same CI configurations for pull requests from forks as for pu…

…ll requests from main repo

.github/workflows/system-tests.yml

@@ -4,6 +4,9 @@ on:
   push:
     branches:
       - "**"
+  pull_request:
+    # The branches below must be a subset of the branches above
+    branches: [ '**' ]
   workflow_dispatch: {}
   schedule:
     - cron:  '00 04 * * 2-6'

.github/workflows/test-head.yaml

@@ -1,5 +1,5 @@
 name: Test unstable
-on: [push]
+on: [push, pull_request]
 jobs:
   test-head:
     strategy:

.github/workflows/test-macos.yaml

@@ -5,7 +5,7 @@ on:
       - "**"
   pull_request:
     # The branches below must be a subset of the branches above
-    branches: [ master ]
+    branches: [ "**" ]
 jobs:
   test-macos:
     strategy:

.github/workflows/test-yjit.yaml

@@ -1,5 +1,5 @@
 name: Test YJIT
-on: [push]
+on: [push, pull_request]
 jobs:
   test-yjit:
     strategy: