Layman can be used to use external portage directories via svn and more different programs and integrate all into portage.

At first we need to install layman:

emerge -av layman

At first create a virtual host in your apache config and place there a config file for layman. overlay.xml Now add to the file /etc/layman/layman.conf the line:

overlays  : http://www.gentoo.org/proj/en/overlays/layman-global.txt
        http://overlay.idefix.lan/overlay.xml

Edit /etc/make.conf

source /usr/portage/local/layman/make.conf

Now we create the xml file on the server:

<?xml version="1.0" ?>
<layman>
        <overlay
            contact = "idefix@fechner.net"
            name = "idefix"
            src  = "http://overlay.idefix.lan/"
            type = "svn"
            status = "official">

                <link>
                        http://overlay.idefix.lan/svn/overlay/trunk/
                </link>

                <description>
                        Idefix overlay.
                </description>
        </overlay>
</layman>