Node Privacy

[alex-courtis]

Nodes should not be exposed to the user. They are internal representations and should not be mutated by the user.

api.tree.get_nodes and sort_by return/are passed cloned partial nodes.

api.tree.get_node_under_cursor returns the internal node. API functions that take {node} expect a real node.

Proposal:

1. add a node identifier like a UUID
2. all API returns a cloned node containing UUID
3. existing api that takes {node} maps to the internal node via identifier

1 may could achieved via absolute_path, similar to sort_by.

[alex-courtis]

This may be achieved before or during a refactor of the {node} consuming API to take {opts}.