bug#19576: write-file writes the wrong buffer

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 17 Nov 2015 09:34:26 +0100
> From: martin rudalics <rudalics@gmx.at>
> Cc: 19576@debbugs.gnu.org
> 
> I attach a fix for restoring current buffer and selected window (the
> latter hopefully taking care of selecting the right frame).  Please tell
> me whether it's sufficient for your purposes.

Thanks for working on this, Martin.  However, I don't think we should
install this change.  We call Lisp hooks from many places, including
maybe a dozen in the display engine.  It makes little sense to make
only one of them resistant to this kind of problems.  OTOH, if we do
this everywhere, I feel that we will unduly punish 99.999% percent of
legitimate users of these hooks just because one of them had a bug.

I think this is a clear bug in follow.el, and should be fixed there,
and nowhere else.  Perhaps we should also have some prominent warnings
in the documentation about this gotcha, so that the probability this
will happen again becomes lower.

Thanks.