Extract to Category refactoring

Groovy-Eclipse can implement a refactoring called "Extract to Category". This refactoring will take an existing method and extract it to a category class. It will convert the method to static and add an additional parameter. This will be similar to the AspectJ "Pull-out" refactoring (and this may be a more appropriate name for the refactoring. Here is an example:

Existing code:

class Flar {
  def blah
  String myMethod(arg1, arg2) {
    this.blah blah.blah
  }
}

Invoking the refactoring will bring up a dialog where you choose which methods to extract (users should be able to choose multiple) and you choose a target type. Final code will look like this:

class Flar {
  def blah
}

// FlarCategory.groovy
class FlarCategory {
  static String myMethod(Flar self, arg1, arg2) {
    self.blah self.blah.blah
  }
}

A tricky piece will be ensuring that references (implicit or not) to this are changed to self references.