Add TreeController.normalizeSelectedNodes and supporting functions in Node.

Frameworks/RSTree/RSTree/Node.swift

@@ -103,6 +103,34 @@ public final class Node: Equatable {
 		}
 		return nil
 	}
+
+	public func hasAncestor(in nodes: [Node]) -> Bool {
+
+		for node in nodes {
+			if node.isAncestor(of: self) {
+				return true
+			}
+		}
+		return false
+	}
+
+	public func isAncestor(of node: Node) -> Bool {
+
+		if node == self {
+			return false
+		}
+
+		var nomad = node
+		while true {
+			guard let parent = nomad.parent else {
+				return false
+			}
+			if parent == self {
+				return true
+			}
+			nomad = parent
+		}
+	}
 }
 
 

Frameworks/RSTree/RSTree/TreeController.swift

@@ -67,6 +67,21 @@ public final class TreeController {
 
 		return nodeInArrayRepresentingObject(nodes: [rootNode], representedObject: representedObject, recurse: true)
 	}
+
+	public func normalizedSelectedNodes(_ nodes: [Node]) -> [Node] {
+
+		// An array of nodes might include a leaf node and its parent. Remove the leaf node.
+
+		var normalizedNodes = [Node]()
+
+		for node in nodes {
+			if !node.hasAncestor(in: nodes) {
+				normalizedNodes += [node]
+			}
+		}
+
+		return normalizedNodes
+	}
 }
 
 private extension TreeController {
@@ -117,5 +132,4 @@ private extension TreeController {
 
 		return childNodesDidChange
 	}
-	
 }