refactor: Separate tree ownership from API. (#300)

* Add TreeInterface, which is the Deref
  target for Tree.

Author: molpopgen

src/lib.rs

@@ -93,6 +93,7 @@ mod site_table;
 mod table_collection;
 mod table_iterator;
 mod traits;
+mod tree_interface;
 mod trees;
 pub mod types;
 mod util;
@@ -437,7 +438,8 @@ pub use traits::IndividualParents;
 pub use traits::NodeListGenerator;
 pub use traits::TableAccess;
 pub use traits::TskitTypeAccess;
-pub use trees::{NodeTraversalOrder, Tree, TreeSequence};
+pub use tree_interface::{NodeTraversalOrder, TreeInterface};
+pub use trees::{Tree, TreeSequence};
 
 // Optional features
 #[cfg(any(feature = "provenance", doc))]

src/table_collection.rs

@@ -1119,7 +1119,8 @@ impl TableCollection {
     }
 
     #[cfg(any(doc, feature = "provenance"))]
-    /// Set the provenance table from an [`OwnedProvenanceTable`](`crate::provenance::OwnedSiteTable`)
+    /// Set the provenance table from an
+    /// [`OwnedProvenanceTable`](`crate::provenance::OwnedProvenanceTable`)
     ///
     /// # Errors
     ///