fix: nits from review

Author: faiq

docs/content/customization/nutanix/machine-details.md

@@ -111,7 +111,18 @@ spec:
       vcpusPerSocket: 1
 ```
 
-### (Optional) Use Image template
+### (Optional) Using templates for VM Image lookup:
+
+Users can set format look up the image for a VM, It will be ignored if an explicit image is set.
+Supports substitutions for `{{.BaseOS}}` and `{{.K8sVersion}}` with the base OS and
+kubernetes version, respectively. The BaseOS will be the value in BaseOS and the K8sVersion
+is the value in the Machine `.spec.version`, with the v prefix removed.
+This is effectively the defined by the packages produced by kubernetes/release without v as a
+prefix: 1.13.0, 1.12.5-mybuild.1, or 1.17.3. For example, the default
+image format of `{{.BaseOS}}-?{{.K8sVersion}}-*` and `BaseOS` as "rhel-8.10" will end up
+searching for images that match the pattern rhel-8.10-1.30.5-* for a
+Machine that is targeting Kubernetes version `v1.30.5`. See
+also: https://golang.org/pkg/text/template/
 
 ```yaml
 apiVersion: cluster.x-k8s.io/v1beta1

pkg/handlers/nutanix/mutation/machinedetails/inject.go

@@ -5,6 +5,7 @@ package machinedetails
 
 import (
 	"context"
+	"errors"
 	"slices"
 
 	apiextensionsv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
@@ -32,6 +33,8 @@ type nutanixMachineDetailsPatchHandler struct {
 	patchSelector     clusterv1.PatchSelector
 }
 
+var ErrNoImageOrImageLookupSet = errors.New("image or image lookup must be set")
+
 func newNutanixMachineDetailsPatchHandler(
 	metaVariableName string,
 	variableFieldPath []string,
@@ -98,6 +101,8 @@ func (h *nutanixMachineDetailsPatchHandler) Mutate(
 				spec.Image = nutanixMachineDetailsVar.Image.DeepCopy()
 			} else if nutanixMachineDetailsVar.ImageLookup != nil {
 				spec.ImageLookup = nutanixMachineDetailsVar.ImageLookup.DeepCopy()
+			} else {
+				return ErrNoImageOrImageLookupSet
 			}
 
 			spec.VCPUSockets = nutanixMachineDetailsVar.VCPUSockets

test/e2e/data/shared/v1beta1-capx/metadata.yaml

@@ -10,9 +10,6 @@
 apiVersion: clusterctl.cluster.x-k8s.io/v1alpha3
 kind: Metadata
 releaseSeries:
-  - major: 1
-    minor: 5
-    contract: v1beta1
   - major: 1
     minor: 6
     contract: v1beta1