bug#56518: Drop rsh/rlogin/remsh from Ange FTP

[Michael Albinus <michael.albinus@gmx.de>]

Stefan Kangas <stefan@marxist.se> writes:

Hi Stefan,

> Assuming that Ange FTP is still relevant these days, its documentation
> should not be talking about using "rsh", "rlogin" and "remsh" (as they
> are obsolete).  Please rewrite its documentation to talk about SSH
> instead.

These programs are mentioned in relation to "gateways". That is, if you
cannot access the FTP server from your local machine, you can connect to
that gateway (via rsh or alike) and start the ftp client on that
machine.

I guess we shall remove gateways at all from ange-ftp.el, because I
don't know whether they work with ssh or friends. At least, they shall
be made obsolete.

A proper replacement would be to improve Tramp's multi-hop, and support
remote file names like "/ssh:gateway|ftp:server:/path/to/file". Anything
goes, but is it really worth the trouble? It won't be trivial.

OTOH, I have no idea whether there's still somebody using Ange FTP with
gateways.

> (I note that Firefox and Chrome dropped FTP support in 2021.
> And the FSF has sunset their FTP servers.)

Sigh.

Best regards, Michael.