From 2df7196c00856df6b7e25e8ec181e37e8eba28de Mon Sep 17 00:00:00 2001
From: Patrick Cloke <patrickc@matrix.org>
Date: Thu, 10 Jun 2021 08:32:46 -0400
Subject: [PATCH] Manually pull the complement branch matching the current
 branch name.

---
 .github/workflows/tests.yml | 11 ++++++-----
 changelog.d/10160.misc      |  1 +
 2 files changed, 7 insertions(+), 5 deletions(-)
 create mode 100644 changelog.d/10160.misc

diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 7c2f7d4b1301..f6e880a74e18 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -305,11 +305,12 @@ jobs:
         with:
           path: synapse
 
-      - name: Run actions/checkout@v2 for complement
-        uses: actions/checkout@v2
-        with:
-          repository: "matrix-org/complement"
-          path: complement
+      # Attempt to check out the same branch of Complement as the PR. If it
+      # doesn't exist, fallback to master.
+      - name: Checkout complement
+        run: |
+          mkdir -p complement
+          (wget -O - https://github.com/matrix-org/complement/archive/$GITHUB_HEAD_REF.tar.gz || wget -O - https://github.com/matrix-org/complement/archive/master.tar.gz) | tar -xz --strip-components=1 -C complement
 
       # Build initial Synapse image
       - run: docker build -t matrixdotorg/synapse:latest -f docker/Dockerfile .
diff --git a/changelog.d/10160.misc b/changelog.d/10160.misc
new file mode 100644
index 000000000000..80f378130f32
--- /dev/null
+++ b/changelog.d/10160.misc
@@ -0,0 +1 @@
+Fetch the corresponding complement branch when performing CI.