bug#5840: 24.0.50; wrong tramp-file-name-regexp

[Stefan Monnier <monnier@iro.umontreal.ca>]

>> with these settings:
>> 
>> ,----
>> | (add-hook 'minibuffer-setup-hook
>> |           (lambda () (add-hook 'post-command-hook
>> |                                'minibuffer-completion-help nil t)))
>> `----
>> 
>> If you do:
>> C-x C-f ==> /su:
>> 
>> You have not the time to type the second ":" and tramp fail.
>> (same for ssh/ftp)

While I do get a Tramp failure, indeed, this does not prevent me from
typing the second :.  I think the problem is more that the Tramp error
is very loud and makes you think it's the end of the world, whereas in
reality Emacs is still there waiting for you keep on typing.

>> This could be fixed by modifying tramp-file-name-regexp like this:
>> (tramp-file-name-regexp "\\`/\\([^[/:]+\\|[^/]+]\\):.*:")
> This would be wrong. "/hostname:/path" is a valid remote file name, which
> would not be catched by your regexp.
> (For the records, I also dislike Tramp's syntactic ambiguity. But this is
> history, I guess we cannot change it anymore.)

Everything can be changed.

> In order to fix this problem, one could tweak
> `minibuffer-completion-predicate' in `minibuffer-completion-help',
> which is `file-exists-p' in the given case.

I think we somehow need to make the error a bit more quiet.
Most of it needs to be done on Tramp's side, but maybe we can help it by
having the completion code warn Tramp that this is only used
for completion.  Or maybe the completion code can catch the error and
just display it calmly.

I wonder, tho: why is Tramp so loud?  Shouldn't it just call `signal'
with appropriate parameters to indicate an error, without popping up
any window?


        Stefan