Index: config/locales/en.yml
===================================================================
--- config/locales/en.yml       (revision 3358)
+++ config/locales/en.yml       (working copy)
@@ -276,6 +276,7 @@
   field_content: Content
   field_group_by: Group results by
   field_sharing: Sharing
+  field_relations_from: Duplicated by

   setting_app_title: Application title
   setting_app_subtitle: Application subtitle
Index: app/models/query.rb
===================================================================
--- app/models/query.rb (revision 3358)
+++ app/models/query.rb (working copy)
@@ -195,7 +195,9 @@
     if User.current.logged?
       @available_filters["watcher_id"] = { :type => :list, :order => 15, :values => [["<< #{l(:label_me)} >>", "me"]] }
     end
-
+    # filter out duplicates
+    @available_filters["relations_from"] = { :type => :list, :order => 14, :values => [ ["none", "none"] ] }
+
     if project
       # project specific filters
       unless @project.issue_categories.empty?
@@ -395,6 +397,11 @@
         db_field = 'user_id'
         sql << "#{Issue.table_name}.id #{ operator == '=' ? 'IN' : 'NOT IN' } (SELECT #{db_table}.watchable_id FROM #{db_table} WHERE #{db_table}.watchable_type='Issue' AND "
         sql << sql_for_field(field, '=', v, db_table, db_field) + ')'
+      elsif field == 'relations_from'
+        # filter out duplicates
+        db_table = IssueRelation.table_name
+        db_field = 'issue_from_id'
+        sql << "#{Issue.table_name}.id NOT IN (SELECT #{db_table}.issue_from_id from #{db_table} where relation_type='duplicates')"
       else
         # regular field
         db_table = Issue.table_name