Clean up after tree construction.

src/GitHub.Unity/Assets/Plugins/GitHub/Editor/Views/BranchesView.cs

@@ -91,6 +91,7 @@ namespace GitHub.Unity
 		void OnRemoteBranchesUpdate(IEnumerable<GitBranch> list)
 		{
 			BuildTree(newLocalBranches, list);
+			newLocalBranches.Clear();
 		}