store path elements or the item itself in the tree

core/src/main/groovy/com/muwire/core/collections/FileCollection.groovy

@@ -37,7 +37,7 @@ class FileCollection {
         name = files.first().pathElements.first()
         tree = new PathTree(name)
         for(FileCollectionItem item : files) {
-            tree.add(item.pathElements)
+            tree.add(item.pathElements, item)
         }
         
         byte [] signablePayload = signablePayload()
@@ -73,7 +73,7 @@ class FileCollection {
         name = files.first().pathElements.first()
         tree = new PathTree(name)
         for(FileCollectionItem item : files) {
-            tree.add(item.pathElements)
+            tree.add(item.pathElements, item)
         }
         
         this.hashCode = Objects.hash(timestamp, author, comment, files)

core/src/main/groovy/com/muwire/core/collections/PathTree.groovy

@@ -10,7 +10,7 @@ class PathTree {
         keyToNode.put(this.root.key(), this.root)
     }
 
-    void add(List<String> paths) {
+    void add(List<String> paths, FileCollectionItem item) {
         PathNode current = null
         for (String path : paths) {
             if (current == null) {
@@ -28,7 +28,9 @@ class PathTree {
                 current.children.add(child)
             }
             current = keyToNode.get(childKey)
+            current.userObject = path
         }
+        current?.userObject = item
     }
     
     public void traverse(Callback cb) {
@@ -51,6 +53,7 @@ class PathTree {
         final PathNode parent
         final Set<PathNode> children = new LinkedHashSet<>()
         private final int hashCode
+        Object userObject
 
         PathNode(String path, PathNode parent) {
             this.parent = parent