merge_tree: test merging new root (parent to h.d)
merge_tree: test merging new root (parent to h.d)

new roots are items with parents that connect to previously deleted
items. This prevents problems with connecting multiple DAGs that may
arise if an item is deleted and a new root without parents would
have been inserted.

Netsend/PerspectiveDB,Netsend/persdb,Netsend/PerspectiveDB,Netsend/persdb,Netsend/persdb,Netsend/PerspectiveDB