From 0a16989d261d0dda2c9b206c333078e3e0e2994d Mon Sep 17 00:00:00 2001
From: Robin <robin@robin.town>
Date: Mon, 28 Mar 2022 08:17:04 -0400
Subject: [PATCH] Fix unexpected coverage diffs for PRs that aren't up to date
 (#8161)

---
 .github/workflows/test_coverage.yml | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/.github/workflows/test_coverage.yml b/.github/workflows/test_coverage.yml
index 292b8a9865..6eb4d883bd 100644
--- a/.github/workflows/test_coverage.yml
+++ b/.github/workflows/test_coverage.yml
@@ -12,6 +12,11 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v2
+        with:
+          # If this is a pull request, make sure we check out its head rather than the
+          # automatically generated merge commit, so that the coverage diff excludes
+          # unrelated changes in the base branch
+          ref: ${{ github.event.type == 'PullRequestEvent' && github.event.pull_request.head.sha || '' }}
 
       - name: Yarn cache
         uses: c-hive/gha-yarn-cache@v2