bug#12314: 24.2.50; `add-to-history': use `setq' with `delete'

[Eli Zaretskii <eliz@gnu.org>]

> From: "Drew Adams" <drew.adams@oracle.com>
> Cc: <cyd@gnu.org>, <12314@debbugs.gnu.org>
> Date: Sat, 8 Sep 2012 08:48:53 -0700
> 
> > I'm not sure who is missing what.  All I'm saying is that the manual
> > seems to suggest that an explicit assignment is unnecessary, and yet
> > Chong did exactly that.  If just "(delete 'foo bar)", with 'bar' a
> > list, is sometimes not enough, the manual should say when.  And if it
> > is enough, why should we make the change in add-to-history?
> 
> It is not enough, if you need the variable to reflect the updated list contents.

Then the manual should be corrected to state that much more explicitly
than it does now.  Perhaps it shouldn't even talk about destructive
removal, as that will surely spread confusion.  For me "destructive"
means "in-place", and no amount of describing how 'delete' works
internally will ever be able to countermand that.  Besides, if all I
need is a quick reminder about the semantics, I'm unlikely to read all
the verbiage, let alone go up to read more under 'delq'.  So the most
important facts should be right there at the beginning, not hidden
away under "note that" etc.