--- redmine-2.3.0-ori/app/models/issue_relation.rb	2014-09-18 17:11:51.380167822 +0200
+++ redmine-2.3.0/app/models/issue_relation.rb	2014-09-18 17:35:08.575357563 +0200
@@ -42,6 +42,8 @@
   TYPE_FOLLOWS      = "follows"
   TYPE_COPIED_TO    = "copied_to"
   TYPE_COPIED_FROM  = "copied_from"
+  TYPE_MIRRORS      = "mirror"
+  TYPE_MIRRORED     = "mirrored"
 
   TYPES = {
     TYPE_RELATES =>     { :name => :label_relates_to, :sym_name => :label_relates_to,
@@ -61,7 +63,11 @@
     TYPE_COPIED_TO =>   { :name => :label_copied_to, :sym_name => :label_copied_from,
                           :order => 8, :sym => TYPE_COPIED_FROM },
     TYPE_COPIED_FROM => { :name => :label_copied_from, :sym_name => :label_copied_to,
-                          :order => 9, :sym => TYPE_COPIED_TO, :reverse => TYPE_COPIED_TO }
+                          :order => 9, :sym => TYPE_COPIED_TO, :reverse => TYPE_COPIED_TO },
+    TYPE_MIRRORS =>      { :name => :label_mirror, :sym_name => :label_mirrored,
+                          :order => 10, :sym => TYPE_MIRRORED, :reverse => TYPE_MIRRORED },
+    TYPE_MIRRORED =>      { :name => :label_mirrored, :sym_name => :label_mirror,
+                          :order => 11, :sym => TYPE_MIRRORS, :reverse => TYPE_MIRRORS }
   }.freeze
 
   validates_presence_of :issue_from, :issue_to, :relation_type