I’m too tired to go too deep into the changes in the kdesrc-build 1.13 release, but the largest is that module data from projects.kde.org can now be used to build git modules.
Obviously kdesrc-build was already perfectly capable of finding git modules, so this isn’t very useful if you’re already building everything you want to be building. However, what the module database gives you is categorization and grouping (without git submodules, which kdesrc-build doesn’t support at all yet). e.g. if in theory you asked for extragear/graphics, which is not a real git module, kdesrc-build would figure out you wanted Digikam, kipi-plugins, Skanlite, and KGraphViewer.
The larger the groupings become, the more useful this feature becomes. There are many other minor fixes/changes/bugfixes to go with it (including the first release of a test suite, although it is still pitifully small). As always, please let me know if I’ve messed something up!