bug#17453: Isearch doesn't work properly with Follow Mode.

[Eli Zaretskii]

> Date: Mon, 2 Nov 2015 15:44:45 +0000
> From: Alan Mackenzie <acm@muc.de>
> Cc: Juri Linkov <juri@linkov.net>, 17453@debbugs.gnu.org,
>       emacs-devel <emacs-devel@gnu.org>
> 
> A related point in one of your patches below.  It explicitly selects one
> of the Follow Mode windows.  This is bad.  Follow Mode itself choses the
> right window in its post-command-hook.  Second-guessing it within the
> command processing is liable to lead to confusion, maintenance
> difficulties, and general pain.

You could call the same code that post-command-hook calls, then it
wouldn't be second-guessing.