bug#60587: Patch for adding links to symbols' help documentation

[Drew Adams]

> > 2. Instead of putting it on the hook when loading
> > the code, add/remove it in a :set function.  E.g.
> > (untested):...
> >
> > 3. Maybe add a toggle command for the option, so
> > users can switch the behavior anytime, on the fly.
> 
> What about using `add-variable-watcher'?

Did you mean for #2: when/where to add the function
to the hook?  Or did you mean use a watcher instead
of #3, a toggle command?

Assuming you meant #2:

Also possible.  Seems a bit overkill to me, though.

This is what :set is for, for options.  A variable
watcher can do anything, not just for an option,
and not just when the var is set.