Add MergeRequest#target_project_namespace

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/models/merge_request.rb

@@ -253,6 +253,14 @@ class MergeRequest < ActiveRecord::Base
     end
   end
 
+  def target_project_namespace
+    if target_project && target_project.namespace
+      target_project.namespace.path
+    else
+      "(removed)"
+    end
+  end
+
   def source_branch_exists?
     return false unless self.source_project