Writing rules for the conversion from SVN to Git requires you to download the whole SVN repository. Its full size is currently 65GB, which is a problem for a lot of our developers. Hence we have setup a server which can be used for the rule writing (used to be three).
Every registered KDE developer has access to the server with the keys you have setup on identity.kde.org.
This document assumes you are familiar with the rule writing. A good document to learn more about that can be found at http://techbase.kde.org/Projects/MoveToGit/UsingSvn2Git