bug#10289: 24.0.92; Sneaky clobbering of user key binding

[Stephen Berman <stephen.berman@gmx.net>]

I was reading gnu-emacs-help with Gnus, and one of the articles included
a MIME part of type "text/x-org", which results in org-mode being
called, which loads a slew of org libraries.  Some time later I went to
the Calendar and typed `k', which is unbound in the default Calendar and
Diary mode maps, but which I have bound to a command I defined.
However, this time my command wasn't called, but instead
org-agenda-action.  This is due to the defcustom
org-calendar-agenda-action-key in org.el, which is set to `k' by default
and was enabled when I read the article with the text/x-org MIME part.

I think it's a bug to clobber a user setting in this sneaky way: I don't
use Org, so I didn't know about this binding or the defcustom that sets
it.  But even if I did know, it seems rather nasty to be forced to set a
variable to avoid clobbering a setting I had no reason to expect to be
problematic.

I think the best solution to this problem from the user's POV would be
to prevent the processing of a MIME part from effecting other buffers,
perhaps by unloading the libraries after the processing (unless they
were already loaded before the article was opened); or would that
throttle Emacs too much?  If so, a less desirable solution could be for
defcustoms like org-calendar-agenda-action-key to check whether the key
is bound and in that case require (as nonintrusively as possible) user
intervention.


In GNU Emacs 24.0.92.2 (i686-suse-linux-gnu, GTK+ Version 2.24.7)
 of 2011-12-05 on escher
Windowing system distributor `The X.Org Foundation', version 11.0.11004000
configured using `configure  '--without-toolkit-scroll-bars' 'CFLAGS=-g''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US.UTF-8
  value of $XMODIFIERS: @im=local
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t