no way to patch the debian/ folder in os-specific debian branches

PCL is a good example.
A file has to be patched for the Raspbian (wheezy), but not for other distributions.
One would want to write a patch in debian/patches for this case, and have bloom add it to the debian files generated from the debian/groovy/pcl branch, just for the debian/groovy/wheezy/pcl branch, and not for the others.