From ea5104f565a9ebbb0b9cc5e13ca69d760e22a522 Mon Sep 17 00:00:00 2001
From: Victor Lin <13424970+victorlin@users.noreply.github.com>
Date: Wed, 20 Dec 2023 12:02:08 -0800
Subject: [PATCH] Limit concurrent CI runs

Concurrent runs often happen due to iterative pushes to a PR. In those
cases, only the most recent commit is useful for CI to run.

Given current concurrency limitations, I've been in situations where the
most recent commit to a PR was waiting for CI runs on older commits to
finish before it could even start, due to the FIFO nature of GitHub
Actions workflow run scheduling. In those situations, I've manually
canceled the older CI runs to allow the most recent CI to run. This
change automates that process.

Concurrent CI runs on the default branch are useful, so those are still
allowed.
---
 .github/workflows/ci.yaml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index c0b82a2c8..d0ced341d 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -13,6 +13,11 @@ on:
 
   workflow_dispatch:
 
+# Prevent concurrent runs on the same branch, except for the default branch.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}-${{ github.ref_type == 'branch' && github.ref_name == github.event.repository.default_branch && github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   pytest-cram:
     name: test (python=${{ matrix.python-version }} biopython=${{ matrix.biopython-version || 'latest' }})