When creating a new issue by copying from an existing one, the @new@ form will only allow to change between two status (the default one and the status from the existing issue). The commit who implemented this feature is r9404.

What is the reasoning behind this? When I copy an issue, I'm interested in the text and the properties but I would like to be able to choose between all the status which are normally available to me when I create a new issue without copying.