Prevent concurrent builds per branch (#1178)

* Cancel concurrent test jobs when new push occurs

Author: BryanFauble

.github/workflows/build.yml

@@ -27,6 +27,12 @@ on:
     types:
       - 'published'
 
+# Cancel any previous runs of this workflow that are still in progress.
+# This is to avoid running the same tests multiple times concurrently.
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
 
   pre-commit:
@@ -38,7 +44,6 @@ jobs:
         python-version: '3.13'
     - uses: pre-commit/[email protected]
 
-
   # run unit (and integration tests if account secrets available) on our build matrix
   test:
     needs: [pre-commit]