refactor preset validation

cmd/root.go

@@ -45,16 +45,29 @@ func checkStdin() error {
 }
 
 /*
- * validatePresets performs some basic checks on the presets passed in and
+ * validatePreset performs some basic checks on the preset passed in and
  * returns an error if it finds a problem.
  */
+func validatePreset(preset string) error {
+	info, err := os.Stat(preset)
+	if err != nil {
+		return err
+	} else if info.IsDir() {
+		return errors.New("preset " + preset + " is a directory")
+	}
+
+	return nil
+}
+
+/*
+ * validatePresets validates each preset passed in and returns an error if it
+ * finds a problem.
+ */
 func validatePresets(cmd *cobra.Command, args []string) error {
 	for _, p := range args {
-		info, err := os.Stat(p)
+		err := validatePreset(p)
 		if err != nil {
 			return err
-		} else if info.IsDir() {
-			return errors.New("preset " + p + " is a directory")
 		}
 	}