bug#18891: Doesn't handle pwd = /C: very well

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Date: Tue, 04 Nov 2014 11:47:19 -0500
> Cc: 18891@debbugs.gnu.org
> 
> Michael Albinus wrote:
> 
> >    "/C:" as default directory is wrong. It triggers Tramp to start,
> >    which fails. Maybe one could prevent this problem by giving the
> >    default directory the prefix "/:".
> 
> You know much more about this than I do, but my dumb idea was:
> if a directory name happens to match a tramp pattern, as "/C:"
> presumably does, how about first checking if a local directory literally
> named that exists, before invoking a remote handler?

That's probably something Emacs should do _before_ invoking the
handler, no?  I mean, the decision whether to let the handler do this
job is outside the scope of the handler.