Codechange: Add format_append as short-hand to format_to + back_inserter.

src/core/format.hpp

@@ -45,4 +45,10 @@ struct fmt::formatter<T, Char> : fmt::formatter<typename T::BaseType> {
 	}
 };
 
+template <class... Args>
+void format_append(std::string &out, fmt::format_string<Args...> &&fmt, Args&&... args)
+{
+	fmt::format_to(std::back_inserter(out), std::forward<decltype(fmt)>(fmt), std::forward<decltype(args)>(args)...);
+}
+
 #endif /* FORMAT_HPP */