RE: Introducing thread-safe Tramp

[Drew Adams]

> The variable sets a default. But sometimes, I want to visit a file sync
> or async the other way the default tells. It is a simple approach to
> overwrite the default ad-hoc, w/o fiddling with the variable customization.

I understood that. That was the starting point (with your initial desire to use 
a prefix arg with the standard file commands), and it's a common use of a 
prefix arg. I agree with such toggling. (In fact, I'm in favor of even toggling 
user options this way, which is considered a no-no here.)

> And it has the advantage that it works both "C-x & C-x C-f ..." and
> "C-x & M-x find-file ...". No new key bindings, no new commands. I
> regard this as essential advantage, given my poor memory muscle ...

I understood that.

> > Not sure what to think about the `C-x &' proposal. It certainly is
> > interesting, though - seems even generally promising. We've never
> > taken such an approach before, have we (dunno)? Is there a new need?
> > Or is this discovery of a helpful, general new feature? Seems like the
> > latter. (Could be both.) Perhaps this deserves some new terminology
> > and general doc.
> 
> I propose we just start with it, and see how it works. Emacs 27 is years
> away, there's much time for improvement.

You didn't answer wrt why we shouldn't just define additional commands and let 
users create async/sync toggle commands using them (and binding them to the 
same muscle-memory keys), or why we shouldn't also create such toggle commands 
(toggling with a prefix arg), but not necessarily bind them to the standard 
keys right away. IOW, what we usually do.

> > (Someone will probably point out that this is nothing special/new, and
> > that I just haven't had enough coffee this morning...)
> 
> Indeed, you miss coffee :-) I have stolen this from
> `universal-coding-system-argument' ("C-x <RET> c ..."), as suggested by Eli.

Right. But this is still a new use case, I think. The `C-x RET c' case is 
pretty much the only other use of this technique, AFAIK.

We document the use of prefix keys, i.e., binding a key to a keymap. We don't 
document this technique/cliche. Perhaps we should.