Rewrite fs::get_parent_dir

Don't analyse full path if possible.

Utilities/File.cpp

@@ -322,12 +322,53 @@ std::shared_ptr<fs::device_base> fs::set_virtual_device(const std::string& name,
 
 std::string fs::get_parent_dir(const std::string& path)
 {
-	// Get (basically) processed path
-	const auto real_path = fs::escape_path(path);
+	std::string_view result = path;
 
-	const auto pos = real_path.find_last_of(delim);
+	// Number of path components to remove
+	usz to_remove = 1;
 
-	return real_path.substr(0, pos == umax ? 0 : pos);
+	while (to_remove--)
+	{
+		// Trim contiguous delimiters at the end
+		if (usz sz = result.find_last_not_of(delim) + 1)
+		{
+			result = result.substr(0, sz);
+		}
+		else
+		{
+			return "/";
+		}
+
+		const auto elem = result.substr(result.find_last_of(delim) + 1);
+
+		if (elem.empty() || elem.size() == result.size())
+		{
+			break;
+		}
+
+		if (elem == ".")
+		{
+			to_remove += 1;
+		}
+
+		if (elem == "..")
+		{
+			to_remove += 2;
+		}
+
+		result.remove_suffix(elem.size());
+	}
+
+	if (usz sz = result.find_last_not_of(delim) + 1)
+	{
+		result = result.substr(0, sz);
+	}
+	else
+	{
+		return "/";
+	}
+
+	return std::string{result};
 }
 
 bool fs::stat(const std::string& path, stat_t& info)