Re: Emacs Newbie Info Pages

[Eli Zaretskii]

> Date: Sun, 22 Sep 2024 13:37:05 +0100 (BST)
> From: Peter Oliver <p.d.oliver@mavit.org.uk>
> cc: summeremacs@summerstar.me, emacs-devel@gnu.org
> 
> How about a customisation variable apply-defaults-from-emacs-major-version, 
> that would be automatically set to the current version when the init file is 
> written for the first time?  With that in place, defaults in new Emacs 
> versions could be changed more freely, and users could opt-in to updated 
> defaults when/if they’re ready.
> 
> With this, the :version argument to defcustom would no-longer be sufficient, 
> of course.  You’d need, say, a :history argument containing a list of version 
> and default-prior-to-that-version pairs.

This only works with options that use "simple" values.  It doesn't
work when options change together with supporting code, because when
the supporting code is modified or deleted, there's no practical way
for Emacs to revert those changes if the user requests the state of
affairs as in a past version.

So, in addition to the significant increase of the maintenance burden
(to keep :history accurate and up-to-date), we'll have situations that
are impossible to solve this way.