TreeGC, Go 1.9, Update Private Keys.
Go 1.9 is required.
It is now possible to update private keys via the admin API and this was added to the available field masks. The key storage format has not changed so we believe this change is transparent.
Deleted trees are now garbage collected after an interval. This hard deletes them and they cannot be recovered. Be aware of this before upgrading if you have any that are in a soft deleted state.
The Admin RPC API has been extended to allow trees to be undeleted - up to the point where they are hard deleted as set out above.