Re: More convenient default rollback for users

[zhanghj <netjune@163.com>]

Lars Magne Ingebrigtsen <larsi@gnus.org> writes:

> When we introduce behavioural changes in Emacs, we often include a way
> to get back to the old behaviour, and we document this in NEWS etc.
>
> But wouldn't it be nice if we had this in a more convenient,
> cut-and-pastable format?
>
> Imagine you're using Emacs 26 for the first time.  Suddenly you notice
> that when you hit the `hyper z' key, Emacs doesn't florbnoze as it used
> to, but forblizes instead!  You're furious!  So you hit the `C-h R' (for
> rollback) keystroke, and you get a buffer that looks like:
>
> -------------
> ;; To roll back changes between Emacs 26 and Emacs 25.1:
>
> ;; If you want the `hyper z' key still to florbnoze instead of
> ;; forblizing:
> (setq hyper-z-mode 'florbnoze)
>
> ... more setqs here...
>
> ;; To roll back changes between Emacs 25.1 and Emacs 24.3:
>
> ...
> -------------
>
> And then the anger dissipates.  No need to read documentation or
> anything.  Just get back the old behaviour you enjoyed.
>
> (And this would also mean that we could introduce new behaviours more
> often, because rollback would be so trivial for the users.)

I think a UI page like "chrome://flags/" in google chrome is better for
this function. In this page, we can show all compitable options for user
to choose.

For expert user, we can provide a file like emacs-24-compitable.el (with
emacs 25 distribution). After loading the file, all behaviors are the
same as emacs 24. This can also be used by packages.