Only run CI for master/develop branches

Make diff exit with code properly

Author: ian-h-chamberlain

.github/workflows/redcode-ci.yml

@@ -1,10 +1,16 @@
 on:
   push:
+    branches:
+      - master
+      - develop
     paths:
-      - "redcode/**"
+      - redcode/**
   pull_request:
+    branches:
+      - master
+      - develop
     paths:
-      - "redcode/**"
+      - redcode/**
 
 defaults:
   run:
@@ -14,7 +20,10 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [macos-latest, ubuntu-latest, windows-latest]
+        os:
+          - macos-latest
+          - ubuntu-latest
+          - windows-latest
     runs-on: ${{ matrix.os }}
     steps:
     - name: Checkout branch
@@ -28,4 +37,4 @@ jobs:
     - name: Build extension
       run: npm run build
     - name: Verify the build did not modify any files
-      run: git diff-index HEAD -- .
+      run: git diff --exit-code HEAD -- .