HTTPS SSH
To use this overlay, you can edit your /etc/layman/layman.cfg like
this:

------------------------------------------------------------------------

overlays  : http://www.gentoo.org/proj/en/overlays/repositories.xml
            https://bitbucket.org/sortsmill/sortsmill-gentoo-overlay/raw/default/sortsmill-gentoo-overlay.xml

------------------------------------------------------------------------

Then, as root, run

   layman -L
   layman -a sortsmill