dub: Is it possible to extend or specialize configurations ?

[wjoe]

configuration "app" {
   versions "CLI"
   target "executable"
   ...
}

configuration "guiapp" : "app" {
   versions "GUI"
   sourceFiles "source/gui.d"
}

The guiapp should basically inherit the "app" configuration and 
extend/override whatever else is needed/different.