* Implement 'branch_source' as a class method instead of as a

  belongs_to association. AFAIK, there is no way to escape the
  default_scope of the revisable class that only selects rows with
  revisable_is_current==true.

  This means that branch_source will work for any parent, whether it
  is an active object or a revision.

lib/acts_as_revisable/acts/common.rb

@@ -21,10 +21,9 @@ def self.included(base) #:nodoc:
         base.instance_eval do
           define_callbacks :before_branch, :after_branch      
           has_many :branches, (revisable_options.revision_association_options || {}).merge({:class_name => base.name, :foreign_key => :revisable_branched_from_id})
-
-          belongs_to :branch_source, :class_name => base.name, :foreign_key => :revisable_branched_from_id
+
           after_save :execute_blocks_after_save
-        end        
+        end
       end
 
       # Executes the blocks stored in an accessor after a save.
@@ -98,6 +97,18 @@ def branch!(*args)
       def is_branching!(value=true) #:nodoc:
         set_revisable_state(:branching, value)
       end
+
+      # XXX: This should be done with a "belongs_to" but the default
+      # scope on the target class prevents the find with revisions.
+      def branch_source
+        self[:branch_source] ||= if self[:revisable_branched_from_id]
+                                   self.class.find(self[:revisable_branched_from_id],
+                                                   :with_revisions => true)
+                                 else
+                                   nil
+                                 end
+
+      end
 
       # Returns true if the _record_ (not just this instance 
       # of the record) is currently being branched.