automatically cancel CI when new commits are pushed to a PR

Author: carloskiki

.github/workflows/workspace.yml

@@ -16,6 +16,12 @@ env:
   RUSTFLAGS: "-Dwarnings"
   RUSTDOCFLAGS: "-Dwarnings"
 
+# If new code is pushed to a PR branch, then cancel in progress workflows for that PR. Ensures that
+# we don't waste CI time, and returns results quicker https://github.com/jonhoo/rust-ci-conf/pull/5
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   clippy:
     runs-on: ubuntu-latest