User/host name completion: how to deal with ambiguity?

[Kai Großjohann]

The new filename format on Emacs looks like this:

    /method:address@hidden:path

The method and the user can be omitted.  Now Michael has done some
great work on allowing completion on incomplete Tramp filenames.  For
example, if you type

    /ssh:au<TAB>

then you get a list of all host names starting with "au".  Tres
cool.  (Maybe you should also get a list of user names starting
"au".  Not sure if this happens.)

But there is an ambiguity problem.  Take the following filename as an
example:

    /ssh:

It could be a complete Tramp filename specifying the home directory
on the host ssh, using the default method and the default user.

It could also be a partial Tramp filename specifying the ssh method.

Michael's code now tries to look for all possibilities, so it tries
to open a connection to the host ssh using the default method and the
default user.  This, however, is wont to fail, leaving the user
flabbergasted.

Suggestions?

Ideas:

* If it looks like a method name, assume it's not a host name.  This
  has the nasty consequence that "/flarbl:" works today as a
  filename, but if you then define a new method named "flarbl", then
  things will cease to work.

  On the other hand, /flarbl:~/ is unambiguous for the home dir on
  the host, and it's only two additional characters...

* Before trying to connect, look if the host really exists.  But what
  happens if the host exists and allows connections using ssh, but
  the user doesn't have an account on that host?

kai
-- 
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