example of k8s app generated with help of k8s-lib (https://github.com/k14s/k8s-lib)

commands.txt

$ mkdir my-app && cd my-app
$ git clone https://github.com/k14s/k8s-lib _ytt_lib/github.com/k14s/k8s-lib
$ # create `config.yml` with below contents
$ ytt version
Version: 0.23.0 # <-- must be 0.23.0+
$ ytt -f .
$ ytt -f . | kapp deploy -a my-app -f- -y

config.yml

#@ load("@ytt:template", "template")
#@ load("@ytt:library", "library")

#@ def config(port=80):
name: hello
port: #@ port
#@overlay/replace
container:
  image: hashicorp/http-echo
  args:
  - #@ "-listen=:" + str(port)
  - -text="hello!"
#@ end

#@ app = library.get("github.com/k14s/k8s-lib/app").with_data_values(config())

--- #@ template.replace(app.eval())

result.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: hello
  labels:
    app.k8s-lib.k14s.io/name: hello
  namespace: default
spec:
  selector:
    matchLabels:
      app.k8s-lib.k14s.io/deployment-name: hello
  replicas: 1
  template:
    metadata:
      labels:
        app.k8s-lib.k14s.io/deployment-name: hello
    spec:
      containers:
      - name: default
        ports:
        - containerPort: 80
        image: hashicorp/http-echo
        args:
        - -listen=:80
        - -text="hello!"
    affinity:
      podAntiAffinity:
        requiredDuringSchedulingIgnoredDuringExecution:
        - labelSelector:
            matchExpressions:
            - key: app.k8s-lib.k14s.io/deployment-name
              operator: In
              values:
              - hello
          topologyKey: kubernetes.io/hostname
---
apiVersion: autoscaling/v2beta1
kind: HorizontalPodAutoscaler
metadata:
  name: hello-hpa
  labels:
    app.k8s-lib.k14s.io/name: hello
  namespace: default
spec:
  scaleTargetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: hello
  minReplicas: 1
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      targetAverageUtilization: 50
---
apiVersion: kapp.k14s.io/v1alpha1
kind: Config
rebaseRules:
- path:
  - spec
  - replicas
  type: copy
  sources:
  - existing
  resourceMatchers:
  - kindNamespaceNameMatcher:
      kind: Deployment
      namespace: default
      name: hello
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: hello-ingress
  labels:
    app.k8s-lib.k14s.io/name: hello
  namespace: default
spec:
  rules:
  - http:
      paths:
      - path: /
        backend:
          serviceName: hello-service
          servicePort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: hello-service
  labels:
    app.k8s-lib.k14s.io/name: hello
  namespace: default
spec:
  ports:
  - port: 80
    protocol: TCP
  selector:
    app.k8s-lib.k14s.io/deployment-name: hello