bug#20020: 25.0.50; `info-display-manual' should reuse existing window where buffer is displayed

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: drew.adams@oracle.com,  20020@debbugs.gnu.org
> Date: Wed, 09 Oct 2019 19:51:29 +0200
> 
> M-: (info-display-manual "Coreutils")
> C-x 2
> C-x b *scratch*
> M-: (info-display-manual "Coreutils")
> 
> You'll now have two windows displaying the same Info buffer, and that
> was what the user didn't want (and I agree that it's not optimal
> behaviour).  In the user's case, it was exacerbated by having the window
> displayed in a different frame, but that's just a detail.

If this is the change, then I think it should be an opt-in change.  We
don't behave like that with any other buffers, why should Info buffers
be an exception by default?