bug#41705: 28.0.50; minibuffer completion of ".../*/*" shouldn't be "...//"

[Eli Zaretskii]

> From: Pip Cet <pipcet@gmail.com>
> Date: Thu, 04 Jun 2020 09:35:12 +0000
> 
> ./emacs -Q
> enter: C-x C-f * / * <tab>
> 
> expected result: a list of sub-subdirectories of the emacs src dir. A
> "Find file: .../emacs/src/*/" prompt.
> 
> actual result: prompt says "Find file: .../emacs/src//", further tab
> completion uses the root directory.
> 
> I'd noticed this for a while now, but thought it was a local
> configuration issue. It happens in emacs -Q, too, though.
> 
> For master, we should fix minibuffer.el properly, but I'm not sure what
> to do on emacs-27. It's a regression (from Emacs 26) that might annoy
> many users of tab completion in the minibuffer.

Can you bisect to find which commit broke this?

Thanks.