lib/fmt/ToBuffer: add overload with StringBuffer parameter

src/lib/fmt/ToBuffer.hxx

@@ -11,17 +11,40 @@
 #endif
 
 template<std::size_t size>
-[[nodiscard]] [[gnu::pure]]
-auto
-VFmtBuffer(fmt::string_view format_str, fmt::format_args args) noexcept
+StringBuffer<size> &
+VFmtToBuffer(StringBuffer<size> &buffer,
+	     fmt::string_view format_str, fmt::format_args args) noexcept
 {
-	StringBuffer<size> buffer;
 	auto [p, _] = fmt::vformat_to_n(buffer.begin(), buffer.capacity() - 1,
 					format_str, args);
 	*p = 0;
 	return buffer;
 }
 
+template<std::size_t size>
+[[nodiscard]] [[gnu::pure]]
+auto
+VFmtBuffer(fmt::string_view format_str, fmt::format_args args) noexcept
+{
+	StringBuffer<size> buffer;
+	return VFmtToBuffer(buffer, format_str, args);
+}
+
+template<std::size_t size, typename S, typename... Args>
+StringBuffer<size> &
+FmtToBuffer(StringBuffer<size> &buffer,
+	    const S &format_str, Args&&... args) noexcept
+{
+#if FMT_VERSION >= 90000
+	return VFmtToBuffer(buffer, format_str,
+			    fmt::make_format_args(args...));
+#else
+	return VFmtToBuffer(buffer, fmt::to_string_view(format_str),
+			    fmt::make_args_checked<Args...>(format_str,
+							    args...));
+#endif
+}
+
 template<std::size_t size, typename S, typename... Args>
 [[nodiscard]] [[gnu::pure]]
 auto