bug#38457: 27.0.50; dabbrev-expand regression due to message change

[Eli Zaretskii]

> Date: Tue, 10 Dec 2019 15:19:37 +0800
> From: HaiJun Zhang <netjune@outlook.com>
> Cc: 38457@debbugs.gnu.org, stephen.berman@gmx.net
> 
> I reported the bug #34614.
> 
> I meet the bug(#34614 like) everyday. One common scene: I push a commit with 
> magit. And then open a file
> with C-xC-f, a message (“git finished.”) comes and replace the find-file 
> prompt. I need to press C-g and
> C-xC-f again.

There's no need for something as drastic as C-g.  You could instead
press left-arrow, for example, or some other similarly harmless key.

> This is not a big problem. But minibuffer is a basic UI of emacs. If it 
> always has these bugs, users may think
> that minibuffer is not a good design. 

No one argues against fixing this annoyance.  But the fix should not
cause more problems than the problem it fixes, and it should not
change behavior in incompatible ways.  In addition, we want to start
the Emacs 27 release cycle soon, so we don't want invasive changes in
infrastructure used all over the place.