Improve cache list command

cmd/minikube/cmd/cache_list.go

@@ -26,10 +26,10 @@ import (
 	"k8s.io/minikube/pkg/minikube/constants"
 )
 
-const cacheListFormat = "- {{.CacheImageName}}\n"
+var cacheListFormat string
 
 type CacheListTemplate struct {
-	CacheImageName string
+	CacheImage string
 }
 
 // listCacheCmd represents the cache list command
@@ -52,17 +52,20 @@ var listCacheCmd = &cobra.Command{
 }
 
 func init() {
+	listCacheCmd.Flags().StringVar(&cacheListFormat, "format", constants.DefaultCacheListFormat,
+		`Go template format string for the cache list output.  The format for Go templates can be found here: https://golang.org/pkg/text/template/
+For the list of accessible variables for the template, see the struct values here: https://godoc.org/k8s.io/minikube/cmd/minikube/cmd#CacheListTemplate`)
 	cacheCmd.AddCommand(listCacheCmd)
 }
 
-func cacheList(images map[string]interface{}) error {
-	for imageName := range images {
+func cacheList(images []string) error {
+	for _, image := range images {
 		tmpl, err := template.New("list").Parse(cacheListFormat)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "Error creating list template: %s\n", err)
 			os.Exit(1)
 		}
-		listTmplt := CacheListTemplate{imageName}
+		listTmplt := CacheListTemplate{image}
 		err = tmpl.Execute(os.Stdout, listTmplt)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "Error executing list template: %s\n", err)

cmd/minikube/cmd/config/config.go

@@ -220,18 +220,18 @@ func configurableFields() string {
 }
 
 // ListConfigMap list entries from config file
-func ListConfigMap(name string) (map[string]interface{}, error) {
+func ListConfigMap(name string) ([]string, error) {
 	configFile, err := config.ReadConfig()
 	if err != nil {
 		return nil, err
 	}
-	newImages := make(map[string]interface{})
+	var images []string
 	if values, ok := configFile[name].(map[string]interface{}); ok {
 		for key := range values {
-			newImages[key] = nil
+			images = append(images, key)
 		}
 	}
-	return newImages, nil
+	return images, nil
 }
 
 // AddToConfigMap adds entries to a map in the config file

pkg/minikube/constants/constants.go

@@ -96,6 +96,7 @@ const (
 		"cluster: {{.ClusterStatus}}\n" + "kubectl: {{.KubeconfigStatus}}\n"
 	DefaultAddonListFormat     = "- {{.AddonName}}: {{.AddonStatus}}\n"
 	DefaultConfigViewFormat    = "- {{.ConfigKey}}: {{.ConfigValue}}\n"
+	DefaultCacheListFormat     = "{{.CacheImage}}\n"
 	GithubMinikubeReleasesURL  = "https://storage.googleapis.com/minikube/releases.json"
 	KubernetesVersionGCSURL    = "https://storage.googleapis.com/minikube/k8s_releases.json"
 	DefaultWait                = 20