Fixed feature to preserve the state (expansions and selection) in the 'Files' tab when switching between commits.

Author: johanw1232

src/Views/RevisionFileTreeView.axaml

@@ -8,7 +8,7 @@
              mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
              x:Class="SourceGit.Views.RevisionFileTreeView"
              x:Name="ThisControl">
-  <v:RevisionFileRowsListBox ItemsSource="{Binding #ThisControl.Rows}"
+  <v:RevisionFileRowsListBox x:Name="RevisionFileRowsListBox" ItemsSource="{Binding #ThisControl.Rows}"
                              Background="Transparent"
                              SelectionMode="Single"
                              SelectionChanged="OnRowsSelectionChanged"

src/Views/RevisionFileTreeView.axaml.cs

@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-
+using System.Linq;
 using Avalonia;
 using Avalonia.Collections;
 using Avalonia.Controls;
@@ -9,6 +9,7 @@
 using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.VisualTree;
+using SourceGit.ViewModels;
 
 namespace SourceGit.Views
 {
@@ -249,6 +250,17 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
 
             if (change.Property == RevisionProperty)
             {
+                var selectedNode = _revisionFileRowsListBox?.SelectedItem as RevisionFileTreeNode;
+
+                var expandedObjects = new List<Models.Object>();
+                foreach (var node in _rows)
+                {
+                    if (node.IsExpanded)
+                    {
+                        expandedObjects.Add(node.Backend);
+                    }
+                }
+
                 _tree.Clear();
                 _rows.Clear();
                 _searchResult.Clear();
@@ -280,10 +292,51 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
                 var topTree = new List<ViewModels.RevisionFileTreeNode>();
                 MakeRows(topTree, _tree, 0);
                 _rows.AddRange(topTree);
+
+                _revisionFileRowsListBox ??= this.Find<RevisionFileRowsListBox>("RevisionFileRowsListBox");
+
+                if (_revisionFileRowsListBox is { IsArrangeValid: true })
+                {
+                    RestoreTreeState(expandedObjects, selectedNode);
+                }
+
                 GC.Collect();
             }
         }
 
+        private void RestoreTreeState(List<Models.Object> expandedObjects, RevisionFileTreeNode selectedNode)
+        {
+            for (int i = 0; i < _rows.Count; i++)
+            {
+                var revisionFileTreeNode = _rows[i];
+
+                if (!revisionFileTreeNode.IsFolder)
+                    continue;
+
+                if (expandedObjects.FirstOrDefault(o => o.SHA == revisionFileTreeNode.Backend.SHA || o.Path == revisionFileTreeNode.Backend.Path) != null)
+                {
+                    ToggleNodeIsExpanded(revisionFileTreeNode);
+                }
+            }
+
+            if (selectedNode != null)
+            {
+                foreach (var node in _rows)
+                {
+                    if (node.Backend.SHA != selectedNode.Backend.SHA && node.Backend.Path != selectedNode.Backend.Path)
+                        continue;
+
+                    selectedNode = node;
+                    break;
+                }
+            }
+
+            if (_revisionFileRowsListBox != null)
+            {
+                _revisionFileRowsListBox.SelectedItem = selectedNode;
+            }
+        }
+
         private void OnTreeNodeContextRequested(object sender, ContextRequestedEventArgs e)
         {
             if (DataContext is ViewModels.CommitDetail vm &&
@@ -372,5 +425,6 @@ private void MakeRows(List<ViewModels.RevisionFileTreeNode> rows, List<ViewModel
         private AvaloniaList<ViewModels.RevisionFileTreeNode> _rows = [];
         private bool _disableSelectionChangingEvent = false;
         private List<ViewModels.RevisionFileTreeNode> _searchResult = [];
+        private RevisionFileRowsListBox _revisionFileRowsListBox;
     }
 }