Add a flag to determine tests were called from another workflow (#2887)

If a reusable workflow is called from another workflow, the event_type
in the child workflow is still the same as parent's. This is a known
"feature": https://github.com/actions/runner/discussions/1884

Add a flag to inputs that has default value set to true. This is in turn
set only if the workflow is called from another one, chosing the correct
step for obtaining the OS image.

.github/workflows/test.yaml

@@ -12,6 +12,13 @@ on:
 
   # Called by other workflows (e.g. build.yaml)
   workflow_call:
+    inputs:
+      use-artifact:
+        # Workaround for GH weirdness: https://github.com/actions/runner/discussions/1884
+        description: Download OS image using actions/download-artifact
+        required: false
+        type: boolean
+        default: true
 
 jobs:
   test:
@@ -43,12 +50,12 @@ jobs:
           pip install -r tests/requirements.txt
 
       - name: Download HAOS image
-        if: ${{ github.event_name == 'workflow_dispatch' }}
+        if: ${{ inputs.use-artifact }}
         run: |
           curl -sfL -o haos.qcow2.xz  https://os-artifacts.home-assistant.io/${{github.event.inputs.version}}/haos_ova-${{github.event.inputs.version}}.qcow2.xz
 
       - name: Get OS image artifact
-        if: ${{ github.event_name == 'workflow_call' }}
+        if: ${{ !inputs.use-artifact }}
         uses: actions/download-artifact@v3
         with:
           name: ova-image