sftp Vs scp

[Michael Stone]

On Fri, Jan 25, 2019 at 12:23:16AM +0000, Colin Watson wrote:
>As I noted in
>https://lists.mindrot.org/pipermail/openssh-unix-dev/2019-January/037479.html,
>the protocol involves passing -f or -t options as appropriate, so it's
>perfectly straightforward for the client to speak SFTP while preserving
>the existing server protocol.

potentially even exec'ing a different binary (scp-server or whatever) so 
the bulk of the code lives elsewhere, and is easy to remove (and audit 
the removal) if desired.