enhance: allow drag-drop of item (or folder) anywhere in repo-list (#1459)

Dropping on a non-Group item was not allowed earlier, but now it adds/moves the dragged item into the parent Group (possibly Root) of the drop-target item.

Author: goran-w

src/ViewModels/Welcome.cs

@@ -173,6 +173,25 @@ public void AddRootNode()
                 activePage.Popup = new CreateGroup(null);
         }
 
+        public RepositoryNode FindParentGroup(RepositoryNode node, RepositoryNode group = null)
+        {
+            var collection = (group == null) ? Preferences.Instance.RepositoryNodes : group.SubNodes;
+            if (collection.Contains(node))
+                return group;
+
+            foreach (var item in collection)
+            {
+                if (!item.IsRepository)
+                {
+                    var parent = FindParentGroup(node, item);
+                    if (parent != null)
+                        return parent;
+                }
+            }
+
+            return null;
+        }
+
         public void MoveNode(RepositoryNode from, RepositoryNode to)
         {
             Preferences.Instance.MoveNode(from, to, true);

src/Views/Welcome.axaml.cs

@@ -215,7 +215,7 @@ private void DragOverTreeNode(object sender, DragEventArgs e)
                 if (to == null)
                     return;
 
-                e.DragEffects = to.IsRepository ? DragDropEffects.None : DragDropEffects.Move;
+                e.DragEffects = DragDropEffects.Move;
                 e.Handled = true;
             }
         }
@@ -226,12 +226,15 @@ private void DropOnTreeNode(object sender, DragEventArgs e)
                 return;
 
             var to = grid.DataContext as ViewModels.RepositoryNode;
-            if (to == null || to.IsRepository)
+            if (to == null)
             {
                 e.Handled = true;
                 return;
             }
 
+            if (to.IsRepository)
+                to = ViewModels.Welcome.Instance.FindParentGroup(to);
+
             if (e.Data.Contains("MovedRepositoryTreeNode") &&
                 e.Data.Get("MovedRepositoryTreeNode") is ViewModels.RepositoryNode moved)
             {