Hello Erik, all,
Well, let's start small then. I suggested Carpet since it is smaller than Cactus, or all of the ET. But maybe we should start out even smaller -- maybe with one of the CactusUtils thorns. Let's pick Formaline; this one has a formatting that's different from almost all other thorns anyway, and it doesn't see much development.
I just ran clang-format-3.5 on your branch (which used clang-format-3.6 something) and the results agree. So (assuming I check my commits for unexpected changes) I can use Debian's clang-format.
Yours, Roland