I just committed a small change to ActionContext.java so that it will
remember built-in actions that were overridden by plugins.
Now, you can write plugins that override built-in actions by just
having another <action> with the same name in your actions.xml (as I
did in Optional).
This means I don't need to have a HelpViewerFactory anymore (the
approach I took for changing the way a HelpViewer pops when InfoViewer
is loaded). That class will be removed soon, and I'll have jedit bring
up a HelpViewer the same way as it used to.