No support for direct copying of directories

Copying files when both the source and destination are on the same remote host is fast because tramp does a direct copy in tramp-do-copy-or-rename-file-directly. However there is no such support when copying a directory. When copying directories on a remote host via dired it takes a very long time, A directory that takes 100ms to copy via remote shell takes tramp almost a full minute. It looks like there is only support for direct copying files, not directories. Why is that? It seems like an easy performance win, but I don’t know if there is more complexity to it.

-Troy Hinckley