Files attached on issues tracker becomes inaccessible after transferring a repo to another user (BB-15814)

Files attached to a ticket in the repo's issue tracker become unavailable after the change of repository ownership due to wrong url. Link to the attached file continues to contain the username of the original owner of the repository.

To workaround this, one must manually change the address in the browser to finally get the file, or reattach the file to the tracker manually.