kyverno/examples/mutate/overlay/policy_set_imagePullPolicy.yaml

apiVersion: kyverno.io/v1alpha1
kind: Policy
metadata:
  name: set-image-pull-policy
spec:
  rules:
  - name: set-image-pull-policy
    resource:
      kinds:
      - Deployment
    mutate:
      overlay:
        spec:
          template:
            spec:
              containers:
                # match images which end with :latest   
                - (image): "*:latest"
                  # set the imagePullPolicy to "Always"
                  imagePullPolicy: "Always"