If I get this right, this is exactly the same tarball as with them package decker?

In this case I recommend to make true as a single package, possibly using multibuild to build two flavors from the same source files

It is exactly the same tarball, yes. I didn't know about multibuild, but I just read a little about it. I'll change the decker package to use multibuild to build decker-doc. In the meantime, I'll revoke this request.

Thanks for the advice about multibuild!