repro case

.github/workflows/self-test-multistage-docker-build.yml

@@ -112,6 +112,37 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
+      - name: Auth to GH registry
+        uses: docker/login-action@v1
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - uses: ./
+        name: Build with this action
+        id: build
+        with:
+          context: examples
+          repository: ghcr.io/firehed/actions
+          stages: env, configured
+          server-stage: server
+
+      - name: Print outputs
+        run: |
+          echo "Server: ${{ steps.build.outputs.server-tag }}"
+          echo "Testenv: ${{ steps.build.outputs.testenv-tag }}"
+          echo "Commit: ${{ steps.build.outputs.commit }}"
+
+      - name: Run image
+        run: docker run --rm ${{ steps.build.outputs.server-tag }}
+
+  build-different-context-and-dockerfile:
+    name: Override context and file
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+
       - name: Auth to GH registry
         uses: docker/login-action@v1
         with: