update usage docs

README.md

@@ -19,6 +19,8 @@ You can install a specific release version:
 
 ## Usage
 
+* helm release CHART - Would determine the next tag for the chart and update the Chart.yaml
+* helm release CHART -t 12345 - Would update Chart.yaml and modify values.yaml images.tag to equal 1235
 
 ## Release Logic
 

cmd/root.go

@@ -17,10 +17,11 @@ var tagPath string
 
 // rootCmd represents the base command when called without any subcommands
 var rootCmd = &cobra.Command{
-	Use:   "helm-release",
+	Use:   "helm-release [CHART_PATH]",
 	Short: "Determines the charts next release number",
 	Long: `This plugin will use environment variables and git history to divine the next chart version.
 	It will also optionally update the image tag in the values.yaml file.`,
+	Args: cobra.MinimumNArgs(1),
 	RunE: func(cmd *cobra.Command, args []string) error {
 		dir := "."
 		if len(args) > 0 {