From a conversation with Tim Cross (for context, see the thread "Change
`customize-save-variable' to work under 'emacs -Q'?" on emacs-devel on
> The core issue I see is that -Q is useful mainly because it
> establishes a standard default environment.
> Once we allow local customizations to be applied in this
> environment, this standard base default environment no longer
> exists. This may be fine, provided there is some mechanism that
> makes what has been changed explicit and easy to reproduce.
I think that Customize already provides some function for listing
variables that are not at their default values, both Customized and
"rogue" values. Its output could be added to the bug-reporter's buffer
(maybe it's already there in Emacs, but XEmacs doesn't do that yet).
Perhaps it should be glossed with a comment that only defcustoms can be
listed this way.