project: reorganize the structure of the project.

* remove dotnet-tool.json because the project does not rely on any dotnet tools.
* remove Directory.Build.props because the solution has only one project.
* move src/SourceGit to src. It's not needed to put all sources into a subfolder of src since there's only one project.

src/ViewModels/DeleteRepositoryNode.cs

@@ -0,0 +1,27 @@
+using System.Threading.Tasks;
+
+namespace SourceGit.ViewModels
+{
+    public class DeleteRepositoryNode : Popup
+    {
+        public RepositoryNode Node
+        {
+            get => _node;
+            set => SetProperty(ref _node, value);
+        }
+
+        public DeleteRepositoryNode(RepositoryNode node)
+        {
+            _node = node;
+            View = new Views.DeleteRepositoryNode() { DataContext = this };
+        }
+
+        public override Task<bool> Sure()
+        {
+            Preference.RemoveNode(_node);
+            return null;
+        }
+
+        private RepositoryNode _node = null;
+    }
+}