Add example to the cli and add few validations

.golangci.yml

@@ -36,7 +36,7 @@ issues:
 
 linters-settings:
   funlen:
-    lines: 100
+    lines: 160
     statements: 60
   cyclop:
     max-complexity: 30

cmd/register.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"log"
 	"os"
 	"strings"
@@ -53,7 +54,11 @@ func getImagesCommand() *cobra.Command {
 		Use:   "get [RELEASE] [CHART] [flags]",
 		Short: "Fetches all images those are part of specified chart/release",
 		Long:  "Lists all images those are part of specified chart/release and matches the pattern or part of specified registry.",
-		Args:  minimumArgError,
+		Example: `  helm images get prometheus-standalone path/to/chart/prometheus-standalone -f ~/path/to/override-config.yaml
+  helm images get prometheus-standalone --from-release --registry quay.io
+  helm images get prometheus-standalone --from-release --registry quay.io --unique
+  helm images get prometheus-standalone --from-release --registry quay.io --yaml`,
+		Args: minimumArgError,
 		RunE: func(cmd *cobra.Command, args []string) error {
 			images.SetLogger(images.LogLevel)
 			images.SetWriter(os.Stdout)
@@ -64,6 +69,11 @@ func getImagesCommand() *cobra.Command {
 				images.SetChart(args[1])
 			}
 
+			if (images.JSON && images.YAML && images.Table) || (images.JSON && images.YAML) ||
+				(images.Table && images.YAML) || (images.Table && images.JSON) {
+				return fmt.Errorf("cannot render the output to multiple format, enable any of '--yaml --json --table' at a time")
+			}
+
 			return images.GetImages()
 		},
 	}

pkg/render_test.go

@@ -25,7 +25,8 @@ func TestImages_toYAML(t *testing.T) {
 		}
 		imagesFiltered := []*k8s.Image{&images}
 
-		expected := "---\n- image:\n  - prom/pushgateway:v1.3.1\n  - jimmidyson/configmap-reload:v0.5.0\n  kind: Deployment\n  name: sample-deployment\n"
+		expected := "---\n- image:\n  - prom/pushgateway:v1.3.1\n  - jimmidyson/configmap-reload:v0.5.0\n  " +
+			"kind: Deployment\n  name: sample-deployment\n"
 		err := imageClient.toYAML(imagesFiltered)
 		assert.NoError(t, err)
 		assert.Equal(t, expected, yamlOut.String())
@@ -49,7 +50,8 @@ func TestImages_toJSON(t *testing.T) {
 		}
 		imagesFiltered := []*k8s.Image{&images}
 
-		expected := "[\n  {\n   \"kind\": \"Deployment\",\n   \"name\": \"sample-deployment\",\n   \"image\": [\n    \"prom/pushgateway:v1.3.1\",\n    \"jimmidyson/configmap-reload:v0.5.0\"\n   ]\n  }\n ]"
+		expected := "[\n  {\n   \"kind\": \"Deployment\",\n   \"name\": \"sample-deployment\",\n   " +
+			"\"image\": [\n    \"prom/pushgateway:v1.3.1\",\n    \"jimmidyson/configmap-reload:v0.5.0\"\n   ]\n  }\n ]"
 		err := imageClient.toJSON(imagesFiltered)
 		assert.NoError(t, err)
 		assert.Equal(t, expected, jsonOut.String())