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/Views/AutoFocusBehaviour.cs

@@ -0,0 +1,32 @@
+using Avalonia;
+using Avalonia.Input;
+
+namespace SourceGit.Views
+{
+    public class AutoFocusBehaviour : AvaloniaObject
+    {
+        public static readonly AttachedProperty<bool> IsEnabledProperty =
+            AvaloniaProperty.RegisterAttached<AutoFocusBehaviour, InputElement, bool>("IsEnabled", false, false);
+
+        static AutoFocusBehaviour()
+        {
+            IsEnabledProperty.Changed.AddClassHandler<InputElement>((input, e) =>
+            {
+                if (input.GetValue(IsEnabledProperty))
+                {
+                    input.AttachedToVisualTree += (o, _) => (o as InputElement).Focus(NavigationMethod.Directional);
+                }
+            });
+        }
+
+        public static bool GetIsEnabled(AvaloniaObject elem)
+        {
+            return elem.GetValue(IsEnabledProperty);
+        }
+
+        public static void SetIsEnabled(AvaloniaObject elem, bool value)
+        {
+            elem.SetValue(IsEnabledProperty, value);
+        }
+    }
+}