Developing multiple packages in the same repository

What is the recommended workflow to work on multiple packages that belong to the same repository? An example is POMDPs.jl which consists of POMDPs.jl and the subpackage POMDPTools.jl, which is located at lib/POMDPTools.

If I only want to modify one of the packages I would Pkg.develop("POMDPs") and then check out the latest released version in the local git repo and work with it.

If I additionally Pkg.develop("POMDPTools"), both use the same local git repo and I cannot start developing both from their individual latest released versions. E.g. the latest version for POMDPTools.jl might contain additional commits in POMDPs.jl after the latest released version of POMDPs.jl that make the two local package states incompatible.
This could happen if the main package is developed further for the next release and then a patch is released for the subpackage.