I have a Trac server set up on a secure host. If someone enters in a URL for the host without the https:// the webserver issues a 302 response with a redirect to the URL over a secure connection.
Thus, if I go to: http://myhost/trac/login/
It will redirect to: https://myhost/trac/login/
I've noticed that when I try to login using the Eclipse Trac plugin, it makes a try to the unsecured host even if the trac server has an https URL. I have verified this by watching network dumps from wireshark and looking at my apache logs, which indicate it is connecting without SSL.
On a side note, my server is handing out HTTP 302 responses, the client should be able to interpret those.