diff doesn't work for imported resources?

[AndriiOmelianenko]

hello, I'm trying to create a helm chart for existing resources in the cluster with the least breaking changes as possible. So let's say I have a single resource to import (for simplicity):

$ kubectl get sa sa-test -o yaml
apiVersion: v1
imagePullSecrets:
- name: image-pull-secret
kind: ServiceAccount
metadata:
  name: sa-test
  namespace: test

My steps:

1. install an "empty" chart, with no resources (this is to trick helm diff upgrade to work)
2. import resources with labels/annotations

kubectl annotate $KIND $NAME  meta.helm.sh/release-name=$RELEASE_NAME --overwrite
kubectl annotate $KIND $NAME  meta.helm.sh/release-namespace=$NAMESPACE --overwrite
kubectl label $KIND $NAME  app.kubernetes.io/managed-by=Helm --overwrite

3. run helm diff upgrade and see the differences, to tune my chart/values.

But in my case, I get this:

$ helm diff upgrade test ./microservice -f test.values.yaml --namespace test
test, sa-test, ServiceAccount (v1) has been added:
-
+ # Source: microservice/templates/serviceaccount.yaml
+ apiVersion: v1
+ kind: ServiceAccount
+ metadata:
+   name: sa-test
+   labels:
+     helm.sh/chart: microservice-0.1.0
+     app.kubernetes.io/name: microservice
+     app.kubernetes.io/instance: test
+     app.kubernetes.io/version: "0.1.0"
+     app.kubernetes.io/managed-by: Helm
+ automountServiceAccountToken: true

What am I doing wrong?