Re: unload-feature questions and thoughts

[Richard Stallman]

    unload-feature does this:

     - Remove functions from hooks (those in
    `unload-feature-special-hook') and from `auto-mode-alist'.
     - Remove ELP stuff
     - Remove feature names
     - Restores autoloads
     - Kills local variables
     - (f)?makunbound's symbols
     - Kills timers
     - Deletes the load-history element for the file

    A package-defined FEATURE-unload-hook is run as an alternative to just
    *the first* of these items;

Now I see what you mean.  I am not sure why or whether it was
good to set up this feature as it is.  However, that doesn't
necessarily mean we should just get rid of it or break it.

If we can see that the files which use it use it are in general wrong
and are broken, then we can conclude it doesn't matter if we change
this incompatibly.  If we can see that the files which use it would
still work despite an incompatible change, then that change is ok.
Otherwise, we should make a compatible change.

Davis Herring looked at the various FEATURE-unload-hooks and reported
on their problems.  But the report doesn't directly answer
the two crucial questions above.

Davis, can you look at your previous results and answer those
questions?

People have suggested two ways to make a compatible change.
One is to add FEATURE-unload-function in parallel.
The other is to move the standard code to delete from hooks
into a subroutine which FEATURE-unload-hook can call.

I prefer the latter way.