add -d shorthand for --driver

Author: medyagh

cmd/minikube/cmd/start_flags.go

@@ -229,7 +229,7 @@ func initKubernetesFlags() {
 
 // initDriverFlags inits the commandline flags for vm drivers
 func initDriverFlags() {
-	startCmd.Flags().String("driver", "", fmt.Sprintf("Driver is one of: %v (defaults to auto-detect)", driver.DisplaySupportedDrivers()))
+	startCmd.Flags().StringP("driver", "d", fmt.Sprintf("Driver is one of: %v (defaults to auto-detect)", driver.DisplaySupportedDrivers()))
 	startCmd.Flags().String("vm-driver", "", "DEPRECATED, use `driver` instead.")
 	startCmd.Flags().Bool(disableDriverMounts, false, "Disables the filesystem mounts provided by the hypervisors")
 	startCmd.Flags().Bool("vm", false, "Filter to use only VM Drivers")