Run stack-test regularly to keep cache warm

.github/workflows/build.yml

@@ -9,25 +9,7 @@ concurrency:
   cancel-in-progress: true
 jobs:
   stack-test:
-    name: stack test
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - uses: haskell/ghcup-setup@v1
-        id: ghcup
-        with:
-          stack-hook: true
-      - uses: actions/cache@v4
-        with:
-          path: |
-            ${{ steps.ghcup.outputs.basedir }}
-            ~/.stack
-          key: stack-${{ runner.os }}-${{ hashFiles('stack.yaml') }}
-          restore-keys: |
-            stack-${{ runner.os }}-
-            ${{ runner.os }}-
-      - run: ghcup install stack
-      - run: stack test
+    uses: ./.github/workflows/stack-test.yml
 
   flake-no-push:
     name: flake check (no push)

.github/workflows/cache-warmup.yaml

@@ -0,0 +1,9 @@
+name: biweekly cache warmup
+on:
+  schedule:
+    # Every Monday and Thursday at 11:23 UTC
+    - cron: '23 11 * * mon,thu'
+  workflow_dispatch:
+jobs:
+  stack-test:
+    uses: ./.github/workflows/stack-test.yml

.github/workflows/stack-test.yml

@@ -0,0 +1,25 @@
+# Reusable workflow used by the others. Not called directly usually.
+name: stack test
+on:
+  workflow_call:
+jobs:
+  stack-test:
+    name: stack test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: haskell/ghcup-setup@v1
+        id: ghcup
+        with:
+          stack-hook: true
+      - uses: actions/cache@v4
+        with:
+          path: |
+            ${{ steps.ghcup.outputs.basedir }}
+            ~/.stack
+          key: stack-${{ runner.os }}-${{ hashFiles('stack.yaml') }}
+          restore-keys: |
+            stack-${{ runner.os }}-
+            ${{ runner.os }}-
+      - run: ghcup install stack
+      - run: stack test