Overlaying a variety of kinds of resources

existing-config.yml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: foodb
  namespace: knative-serving
  labels:
    app.kubernetes.io/name: knative-serving
    app.kubernetes.io/version: 1.0
    app.kubernetes.io/component: database
spec: {}

---

apiVersion: v1
kind: Service
metadata:
  name: foos
  namespace: knative-serving
  labels:
    app.kubernetes.io/name: knative-serving
    app.kubernetes.io/version: 1.0
    app.kubernetes.io/component: frontend
spec: {}

---

apiVersion: v1
kind: ThirdPartyCRD
metadata:
  name: beebop
  namespace: knative-serving  
  labels:
    app.kubernetes.io/version: 1.0
spec: {}

overlay.yml

#@ load("@ytt:overlay", "overlay")

#@ def knative_resources():
metadata:
  namespace: knative-serving
  labels:
    app.kubernetes.io/name: knative-serving
#@ end


#@overlay/match by=overlay.subset(knative_resources()), expects="1+"
---
metadata:
  labels:
    app.kubernetes.io/version: 2.0