Make the reusable workflow a reusable action

.github/actions/stack-test/action.yml

@@ -0,0 +1,22 @@
+name: stack test
+description: Build and test with stack
+runs:
+  using: composite
+  steps:
+    - 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
+      shell: bash
+    - run: stack test
+      shell: bash

.github/workflows/build.yml

@@ -10,7 +10,11 @@ concurrency:
   cancel-in-progress: true
 jobs:
   stack-test:
-    uses: ./.github/workflows/stack-test.yml
+    name: stack test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: ./.github/actions/stack-test
 
   flake-check:
     name: flake check and push

.github/workflows/cache-warmup.yaml

@@ -6,4 +6,8 @@ on:
   workflow_dispatch:
 jobs:
   stack-test:
-    uses: ./.github/workflows/stack-test.yml
+    name: stack test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+      - uses: ./.github/actions/stack-test

.github/workflows/stack-test.yml

@@ -1,25 +0,0 @@
-# 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