Add support for variable subsitution in Ingress hosts

pkg/commands/build/testdata/testcase-variable-ref-ingress/in/base/deployment.yaml

@@ -0,0 +1,21 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: nginx
+  labels:
+    app.kubernetes.io/component: nginx
+spec:
+  selector:
+    matchLabels:
+      app.kubernetes.io/component: nginx
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/component: nginx
+    spec:
+      containers:
+      - name: nginx
+        image: nginx:1.15.7-alpine
+        ports:
+        - name: http
+          containerPort: 80

pkg/commands/build/testdata/testcase-variable-ref-ingress/in/base/ingress.yaml

@@ -0,0 +1,18 @@
+apiVersion: extensions/v1beta1
+kind: Ingress
+metadata:
+  name: nginx
+  labels:
+    app.kubernetes.io/component: nginx
+spec:
+  rules:
+  - host: $(DEPLOYMENT_NAME).example.com
+    http:
+      paths:
+      - backend:
+          serviceName: nginx
+          servicePort: 80
+        path: /
+  tls:
+  - hosts:
+    - $(DEPLOYMENT_NAME).example.com

pkg/commands/build/testdata/testcase-variable-ref-ingress/in/base/kustomization.yaml

@@ -0,0 +1,13 @@
+resources:
+- deployment.yaml
+- ingress.yaml
+- service.yaml
+
+vars:
+- name: DEPLOYMENT_NAME
+  objref:
+    apiVersion: apps/v1
+    kind: Deployment
+    name: nginx
+  fieldref:
+    fieldpath: metadata.name

pkg/commands/build/testdata/testcase-variable-ref-ingress/in/base/service.yaml

@@ -0,0 +1,12 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: nginx
+  labels:
+    app.kubernetes.io/component: nginx
+spec:
+  ports:
+  - name: http
+    port: 80
+    protocol: TCP
+    targetPort: http

pkg/commands/build/testdata/testcase-variable-ref-ingress/in/overlay/kustomization.yaml

@@ -0,0 +1,4 @@
+nameprefix: kustomized-
+
+bases:
+- ../base