After splitting a subfolder out into a new repository can you still use the original repo as a remote and cherry-pick
pruned commits to the new repository.
The only option I could think of is getting the filter-branch
the second time, pushing it as a second remote, then cherry-pick
from the second remote to the new repository.
I don't know if this would be the reverse submodules or reverse subtrees.
Git's really flexible about things like this. If your other repo's on a shared filesystem you can even