fs.mv ensures there are 2 arguments

weed/shell/command_fs_mv.go

@@ -36,6 +36,10 @@ func (c *commandFsMv) Help() string {
 
 func (c *commandFsMv) Do(args []string, commandEnv *CommandEnv, writer io.Writer) (err error) {
 
+	if len(args) != 2 {
+		return fmt.Errorf("need to have 2 arguments.")
+	}
+
 	sourcePath, err := commandEnv.parseUrl(args[0])
 	if err != nil {
 		return err