Add support for registering custom fields in Subtask Field Copier

lib/subtask_field_copier.rb

@@ -10,6 +10,9 @@
 
 module SubtaskFieldCopier
 
+  mattr_accessor :registered_fields
+  self.registered_fields = []
+
   def self.setup
    unless IssuesController.ancestors.include?(SubtaskFieldCopier::Patches::IssuesControllerPatch)
       IssuesController.prepend SubtaskFieldCopier::Patches::IssuesControllerPatch

lib/subtask_field_copier/patches/issues_controller_patch.rb

@@ -28,17 +28,15 @@ module SubtaskFieldCopier
             end
             @issue.custom_field_values = cf_values
 
-            # --- COPY CUSTOMER, VEHICLE & ESTIMATE---
-            if @issue.respond_to?(:customer=) && parent_issue.respond_to?(:customer)
-              @issue.customer = parent_issue.customer 
-            end
-            
-            if @issue.respond_to?(:vehicle=) && parent_issue.respond_to?(:vehicle)
-              @issue.vehicle = parent_issue.vehicle 
-            end
-
-            if @issue.respond_to?(:estimate=) && parent_issue.respond_to?(:estimate)
-              @issue.estimate = parent_issue.estimate 
+            # --- COPY REGISTERED FIELDS ---
+            # Iterate over any fields registered by other plugins
+            SubtaskFieldCopier.registered_fields.each do |field|
+              setter = "#{field}="
+              
+              # Use metaprogramming to check if the setter/getter exists, then apply
+              if @issue.respond_to?(setter) && parent_issue.respond_to?(field)
+                @issue.send(setter, parent_issue.send(field))
+              end
             end
           end
         end