bug#34622: Find file prompt should indicate sole completion by appending a blank

[Eli Zaretskii]

> From: 積丹尼 Dan Jacobson <jidanni@jidanni.org>
> Cc: 34622@debbugs.gnu.org
> Date: Wed, 27 Feb 2019 13:20:30 +0800
> 
> >> $ touch /tmp/zzz #new plain file
> >> C-x C-f /tmp/zzz
> 
> EZ> But in this case, the first TAB already says "Sole completion", as you
> EZ> wanted...
> 
> Nope: See, needed two tabs!:
> 
>  C-x C-f [find-file]
>  / [self-insert-command]
>  t [self-insert-command]
>  m [self-insert-command]
>  <tab> [minibuffer-complete]
>  z [self-insert-command]
>  z [self-insert-command]
>  <tab> [minibuffer-complete]
>  <tab> [minibuffer-complete]
>  C-h l [view-lossage]

In the original example you typed 3 z's, not 2.  In that case, a
single TAB is enough.

Anyway, like I said: Emacs being an editor has different design
decisions in these cases.