add IsDirectory() check

shell.go

@@ -60,3 +60,11 @@ func (repo *Repo) Exists(filename string) bool {
 	}
 	return true
 }
+
+func (repo *Repo) IsDirectory() bool {
+	info, err := os.Stat(repo.FullPath)
+	if err != nil {
+		return false
+	}
+	return info.IsDir()
+}