Project Manager: Prohibit duplicating a project into itself

editor/project_manager/project_dialog.cpp

@@ -245,6 +245,35 @@ void ProjectDialog::_validate_path() {
 			}
 		}
 	}
+
+	// Check if the target path is a subdirectory of original when duplicating
+	if (mode == MODE_DUPLICATE) {
+		String base_path = original_project_path;
+		String duplicate_target = target_path;
+
+		// Ensure the paths end with a slash
+		if (!base_path.ends_with("/")) {
+			base_path += "/";
+		}
+
+		if (!duplicate_target.ends_with("/")) {
+			duplicate_target += "/";
+		}
+
+		bool is_subdirectory_or_equal;
+
+		if (d->is_case_sensitive(base_path) || d->is_case_sensitive(duplicate_target)) {
+			is_subdirectory_or_equal = duplicate_target.begins_with(base_path);
+		} else {
+			base_path = base_path.to_lower();
+			String target_lower = duplicate_target.to_lower();
+			is_subdirectory_or_equal = target_lower.begins_with(base_path);
+		}
+
+		if (is_subdirectory_or_equal) {
+			_set_message(TTRC("Cannot duplicate a project into itself."), MESSAGE_ERROR, target_path_input_type);
+		}
+	}
 }
 
 String ProjectDialog::_get_target_path() {