Cancel test runs on PRs if another commit comes in

Author: jessegrabowski

.github/workflows/test.yml

@@ -13,6 +13,13 @@ on:
       - "conda-envs/**"
       - "codecov.yml"
 
+# Cancels all previous workflow runs for pull requests that have not completed.
+concurrency:
+  # The concurrency group contains the workflow name and the branch name for pull requests
+  # or the commit hash for any other events.
+  group: ${{ github.workflow }}-${{ github.event_name == 'pull_request' && github.head_ref || github.sha }}
+  cancel-in-progress: true
+
 jobs:
   ubuntu:
     strategy: