set push event to main branch only, to avoid duplicate workflow runs

Author: emilykl

.github/workflows/build-package.yml

@@ -2,6 +2,8 @@ name: Build
 
 on:
   push:
+    branches:
+      - main
   pull_request:
     types: [opened, reopened, synchronize]
 

.github/workflows/check-formatting.yml

@@ -2,6 +2,8 @@ name: Check Python code formatting
 
 on:
   push:
+    branches:
+      - main
   pull_request:
     types: [opened, reopened, synchronize]
 

.github/workflows/run-percy.yml

@@ -2,6 +2,8 @@ name: Run Percy
 
 on:
   push:
+    branches:
+      - main
   pull_request:
     types: [opened, reopened, synchronize]
   workflow_dispatch:

.github/workflows/run-pytest.yml

@@ -2,6 +2,8 @@ name: Test
 
 on:
   push:
+    branches:
+      - main
   pull_request:
     types: [opened, reopened, synchronize]