bug#17361: Tramp does not save history across sessions.

[Eli Zaretskii]

> From: Michael Albinus <michael.albinus@gmx.de>
> Cc: l26wang@gmail.com,  17361@debbugs.gnu.org
> Date: Mon, 28 Apr 2014 20:05:17 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> So we need to support several sentinels per process.
> >
> > Or a protocol: if you install a sentinel, and another one already
> > exists, call it after yours.
> 
> Yes. But all of the sentinels (or filters) must play the same game
> then.

Indeed, the protocol should be universally enforced.