Improve command package isolation.

pkg/commands/build/testdata/testcase-single-overlay/in/overlay/deployment.yaml

@@ -0,0 +1,15 @@
+apiVersion: apps/v1beta2
+kind: Deployment
+metadata:
+  name: nginx
+spec:
+  template:
+    spec:
+      volumes:
+      - name: nginx-persistent-storage
+        emptyDir: null
+        gcePersistentDisk:
+          pdName: nginx-persistent-storage
+      - configMap:
+          name: configmap-in-overlay
+        name: configmap-in-overlay

pkg/commands/build/testdata/testcase-single-overlay/in/overlay/kustomization.yaml

@@ -0,0 +1,21 @@
+namePrefix: staging-
+commonLabels:
+  env: staging
+  team: override-foo
+patchesStrategicMerge:
+  - deployment.yaml
+bases:
+  - ../package/
+configMapGenerator:
+  - name: configmap-in-overlay
+    literals:
+      - hello=world
+  - name: configmap-in-base
+    behavior: replace
+    literals:
+      - foo=override-bar
+secretGenerator:
+- name: secret-in-base
+  behavior: merge
+  commands:
+    proxy: "printf haproxy"