Installing an overlay in the install space of the underlay.
Is it possible to install an overlay in the same install space as an underlay? For example, if I have a base install from source in /opt/ros/hydro, it might be convenient to extend it with additional packages in an overlayed workspace instead of augmenting the original workspace (which for the desktop-full install has about 250 packages on hydro). If those additional packages are merely dependencies (i.e. I don't intend to modify them) and not specific to one project, installing them on top of the underlay in /opt/ros/hydro would be convenient.