Re: Introducing thread-safe Tramp

[Eli Zaretskii <eliz@gnu.org>]

> From: Filipp Gunbin <fgunbin@fastmail.fm>
> Date: Fri, 27 Jul 2018 22:04:04 +0300
> Cc: Drew Adams <drew.adams@oracle.com>, emacs-devel@gnu.org
> 
> It feels like prefix arg should change the user-visible behaviour of
> the command

We never restrict the use of prefix argument only to some sort of
changes.  Besides, running a command asynchronously does change its
user-visible behavior, and quite significantly so.

> Maybe there could be rules for find-file to use async behavior by
> default, like:
> 
> - When a non-local method is explicitly used (that is, not /sudo)
> 
> - When default-directory is on a remote host
> 
> - When a file being visited is greater than some customizable size

That's even worse, IMO.  We will never be able to second-guess what
users want, and they will want a fire escape even if we succeed in
most cases.

> - When a special command was given before (analogy with `C-x RET c' was
> already mentioned here).

"C-x RET c" runs universal-coding-system-argument, which is akin to
prefix argument, only separate from it.  I do agree that using a
separate argument similar to "C-x RET c" is better, since it binds a
variable to a value, like "C-x RET c" does.