新建和编辑issue时，选择里程碑按创建时间的倒序排列

app/models/issue.rb

@@ -853,7 +853,8 @@ class Issue < ActiveRecord::Base
   def assignable_versions
     return @assignable_versions if @assignable_versions
 
-    versions = project.shared_versions.open.all
+   # versions = project.shared_versions.open.all
+    versions = Version.where(:project_id => project.id, :status => "open").order("created_on desc")
     if fixed_version
       if fixed_version_id_changed?
         # nothing to do
@@ -865,7 +866,7 @@ class Issue < ActiveRecord::Base
         versions << fixed_version
       end
     end
-    @assignable_versions = versions.uniq.sort
+    @assignable_versions = versions.uniq
   end
 
   # Returns true if this issue is blocked by another issue that is still open