BUG: Prevent duplicate builds on pull request, push

When a branch is pushed to the same repository, i.e. not a fork, and a
pull request is made, duplicate builds will be generated for both the
pull request and push. Instead, only generate builds for pull requests
against main and pushes to main.

Author: thewtex

.github/workflows/build-test-package.yml

@@ -1,6 +1,12 @@
 name: Build, test, package
 
-on: [push,pull_request]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
 
 env:
   itk-git-tag: "v5.4.0"

{{cookiecutter.project_name}}/.github/workflows/build-test-package.yml

@@ -1,6 +1,12 @@
 name: Build, test, package
 
-on: [push,pull_request]
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+    branches:
+      - main
 
 jobs:
   cxx-build-workflow: