docs: fix oci-image example, add test + docs

Closes #72

README.md

@@ -252,6 +252,14 @@ When running khelm as kpt function or within a container the `repositories.yaml`
 
 Unlike Helm khelm allows usage of any repository when `repositories.yaml` is not present or `--trust-any-repo` (env var `KHELM_TRUST_ANY_REPO`) is enabled.
 
+### Loading a chart from an OCI registry
+
+Using Helm, you can store a Helm chart as OCI image within a container registry.
+To load a chart from an OCI registry using khelm you can leave the `repository` field empty and specify the container registry/image name within the `chart` field, prefixed with `oci://`.
+When using a chart from an OCI registry, Helm's `repository.yaml` configuration is not used.
+Instead, Docker's `config.json` is used to read private registry credentials from, if any.
+This behaviour is aligned with Helm.
+
 ## Helm support
 
 * Helm 2 is supported by the `v1` module version.

e2e/cli-tests.bats

@@ -39,8 +39,9 @@ teardown() {
 	grep -q myreleasex "$OUT_DIR/manifest.yaml"
 }
 
-@test "CLI should support oci registry" {
-	docker run --rm -u $(id -u):$(id -g) -v "$OUT_DIR:/out" "$IMAGE" template myreleasex oci://public.ecr.aws/karpenter/karpenter \
+@test "CLI should support OCI registry" {
+	docker run --rm -u $(id -u):$(id -g) -v "$OUT_DIR:/out" "$IMAGE" \
+		template myreleasex oci://public.ecr.aws/karpenter/karpenter \
 		--version v0.27.0 \
 		--output /out/manifest.yaml \
 		--debug

e2e/kustomize-plugin-tests.bats

@@ -30,3 +30,7 @@ kustomizeBuild() {
 @test "kustomize vars can overwrite helm values" {
 	kustomizeBuild example/kustomize-var/overlay ' value: changed by kustomization overlay'
 }
+
+@test "kustomize generator should support OCI registry" {
+	kustomizeBuild example/oci-image 'app.kubernetes.io/name: karpenter'
+}

example/oci-image/generator.yaml

@@ -3,6 +3,5 @@ kind: ChartRenderer
 metadata:
   name: karpenter
   namespace: kube-system
-repository: "oci://public.ecr.aws/karpenter"
-chart: karpenter
-version: 0.27.0
+chart: "oci://public.ecr.aws/karpenter/karpenter"
+version: 0.35.0