Smarter CI (#44)

Author: theogf

.github/workflows/CI.yml

@@ -1,9 +1,20 @@
 name: CI
+
 env:
   JULIA_NUM_THREADS: 2
 on:
-  - push
-  - pull_request
+  push:
+    branches:
+      - master
+  pull_request:
+
+
+concurrency:
+  # Skip intermediate builds: always.
+  # Cancel intermediate builds: only if it is a pull request build.
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: ${{ startsWith(github.ref, 'refs/pull/') }}
+
 jobs:
   test:
     name: Julia ${{ matrix.version }} - ${{ matrix.os }} - ${{ matrix.arch }} - ${{ github.event_name }}