Re: always put Customizations in `custom-file', never in `user-init-file'

[Stephen J. Turnbull]

Lennart Borgman (gmail) writes:

 > Then it might be best to avoid automatic migration, but to give a 
 > command to migrate custom data to custom-file.

Well, it's embarrassing to admit, but we really screwed up.  Keeping a
backup of the original .emacs should have been enough.  We didn't.
The thing to be aware of, is that after aborting due to an error,
there are no customizations known to customize, but users will often
save a few customizations so that they can get some work done.  This
will then destroy the customization file (at least in our version of
customize) since a custom-save simply writes out the whole state.
Custom has some protection against doing this automatically, I think,
but the migration code wasn't aware of it, and neither were users.
Ooops!  Tricky, very tricky.

The other thing to note is that this was typically reported by people
using Emacs and trying XEmacs.  Normally you don't have errors in your
init file. :-)

I think separate custom-file and automigration are both good ideas.
Just be aware that (at least in our implementation of custom, but I
think it's probably true of Emacs's, too) there are some ways to go
badly wrong, and be careful to protect the user's init file and
existing customizations.

 > Yes, you are of course right.

In hindsight, yes, but we had to learn that from experience.  The
experience is there, I'd like you to benefit from it.