bug#35300: 27.0.50; emacsclient on remote sessions no longer works

[Óscar Fuentes]

Glenn Morris <rgm@gnu.org> writes:

>     *** emacsclient supports an EMACS_SOCKET_NAME environment variable.
>     If set, it provides the default server socket filename.
>     The command-line emacsclient option --socket-name overrides it.
>
>     *** The Emacs server/client now use $XDG_RUNTIME_DIR/emacs for sockets,
>     if the XDG_RUNTIME_DIR environment variable is defined.
>     This is more secure than the old practice of using TMPDIR.
>     If your client cannot find the server socket, check XDG_RUNTIME_DIR
>     has the same value in both client and server environments.
>     You can use the EMACS_SOCKET_NAME environment variable (see above)
>     to specify a particular socket.

This is an improvement, yes. But I'll like to see even a stronger hint
on the output of emacsclient, once we agree that there is no better
solution than to use XDG_RUNTIME_DIR.

It is unfortunate that this change added more requirements to
emacsclient to work correctly.