bug#49774: 27.1; if diff commands finds no differences then do not pop up a window

[Dmitry Gutov]

On 30.07.2021 14:58, ndame via Bug reports for GNU Emacs, the Swiss army 
knife of text editors wrote:
> Okay, then how about adding a configurable delay before popping up the diff 
> window?
> E.g. if no results arrive within, say, 1 second then a timer pops up the
> window, so the user knows the diff is in progress, but slow.

I was going to suggest a user option that switches to the synchronous 
mode of operation, but the above sounds probably even better.

As long as there is someone willing to implement this.