SCP from STDIN: "-t" option undocumented?

[Michael ODonnell]

Having just now quickly RTFSC and done a few superficial
experiments I conclude that the -t option (mnemonic for "to";
there's also a secret "from" flag -f) is not suitable for
use by humans.  It tells scp that it's in "server" mode and
should expect to communicate with its counterpart using some
undocumented protocol that appears to mix commands and data
in-band via stdin.  That's not the droid you're looking for...