[BGL] Adding one graph to another

I need to add/copy one graph into another, both completely connected, and then create an edge between one vertex in the original graph and a vertex in the one copied into it. The edge/vertex properties needs to be copied as well, and this needs to be fairly efficient. The new edge is straightforward, but is there any functionality for the copy/add operation? (Something like an "add_component" algorithm I guess...) To my understanding both the copy_graph and copy_component algorithms both replace all the content in the target graph. If not, what would be the most efficient way to solve this sort of problem? Cheers, -- Tarjei Knapstad