Would that technique be stackable? Let's say I had a different kind of transformation I wanted to deploy.. Maybe if I did this:

remote_sources(name='proto',  dest=java_protobuf_library,
  sources_target = ':proto-source-set', 
  args= {
      imports = [],
      dependencies = [
       ...
      ],
      platform = '1.7',
      provides = artifact(org='com.squareup.external.protos',
                      name='foo-proto',
                      repo=square,),  # see squarepants/plugin/repo/register.py
  },
)