Simple gist that shows the flexibility of ytt and how it can achieve an intended outcome without impacting other commands.

current-version.yml

#@data/values
#! Note that the file coming out of imgpkg would NOT contain the data/values, you would need to access it with the following CLI command:
#! ytt -f package-template.yaml --data-values-file current-version.yml
#! The data/values is just included here so it'll work properly on ytt playground.

---
apiVersion: imgpkg.carvel.dev/v1alpha1
bundle:
  image: harbor.example.com/imgpkg/charts/secretgen-controller@sha256:e302989e79a3c4f17eb5d101ba1c773ea717cde49b5606ffc6424429d70fb8d0
  tag: v0.5.0
kind: BundleLock

package-template.yaml

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

apiVersion: data.packaging.carvel.dev/v1alpha1
kind: Package
metadata:
  name: #@ "secretgen-controller.example.com.{}".format(data.values.bundle.tag)
  namespace: secretgen-controller
spec:
  refName: secretgen-controller.example.com
  version: #@ data.values.bundle.tag
  releaseNotes: "relevant release notes..."
  licenses:
    - "UNKNOWN"
  template:
    spec:
      fetch:
        - imgpkgBundle:
            image: #@ data.values.bundle.image
      template:
        - ytt:
            paths:
              - config/
        - kbld:
            paths:
              - "-"
              - .imgpkg/images.yml
      deploy:
        - kapp: {}