CI: Update workflow trigger conditions

mrkn · mrkn · commit 1205fa1cc1f8 · 2021-06-20T12:48:35.000+09:00
diff --git a/.github/workflows/ubuntu.yml b/.github/workflows/ubuntu.yml
@@ -1,8 +1,14 @@
 name: CI
 
 on:
-- push
-- pull_request
+  push:
+    branches:
+    - master
+  pull_request:
+    types:
+    - opened
+    - synchronize
+    - reopened
 
 jobs:
   test:
