Only run jobs when relevent

.github/workflows/python-package.yml

@@ -3,11 +3,7 @@
 
 name: Python Package
 
-on:
-  push:
-    branches: [ main ]
-  pull_request:
-    branches: [ main ]
+on: [push, pull_request]
 
 jobs:
   test:
@@ -61,7 +57,12 @@ jobs:
 
   build:
     needs: test
+    if: github.event_name == 'push' && (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags'))
+
     runs-on: ${{ matrix.os }}
+    env:
+      MACOSX_DEPLOYMENT_TARGET: 10_15
+
     strategy:
       matrix:
         python-version: [ 3.7, 3.8, 3.9 ]
@@ -106,6 +107,7 @@ jobs:
 
   publish:
     needs: build
+    if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags')
     runs-on: ubuntu-latest
 
     steps: