bug#50671: 28.0.50; ido-mode *Ido Completions* buffer not compact and rebuilt on second TAB

[Y . E .]

Hello,

Steps to reproduce:
1. emacs -Q
2. C-x C-f ~/.emacs.d/ <TAB>
  - See compact *Completions* buffer.
  - No changes on the second <TAB> hit.
3. M-x ido-mode
4. C-x C-f ~/.emacs.d/ <TAB>
  - See not compact *Ido Completions* buffer.
  - Note the completions list is re-built on the second <TAB> hit.

The expected behavior would be for *Ido Completions* buffer to behave
similarly to the *Completions* buffer: to be compact and not change on
sequential <TAB> hits.


A note:
To fix the compactness issue, I currently use this workaround:
(customize-set-variable
 'display-buffer-alist
   '(("\\*Ido Completions\\*"
      (display-buffer-reuse-window display-buffer-at-bottom)
      (window-height . fit-window-to-buffer))))


Thank you for looking into this.


In GNU Emacs 28.0.50 (build 14, x86_64-apple-darwin18.7.0, NS appkit-1671.60 
Version 10.14.6 (Build 18G9216))
Repository revision: 9ca737c4198c5e7faef7a74de7b1e84b11e1dbeb
Repository branch: master