feature: add history navigation tools

src/Models/CommitNavigationHistory.cs

@@ -0,0 +1,49 @@
+using System.Collections.Generic;
+
+namespace SourceGit.Models
+{
+    public class CommitNavigationHistory
+    {
+        public bool CanGoBack => _position > 0;
+        public bool CanGoForward => _position + 1 < _commits.Count;
+        public string Current => _position >= 0 ? _commits[_position] : null;
+        public string Previous => CanGoBack ? _commits[_position - 1] : null;
+        public string Next => CanGoForward ? _commits[_position + 1] : null;
+
+        public void Visit(string sha)
+        {
+            if (_position >= 0 && _commits[_position] == sha)
+                return;
+
+            _commits.RemoveRange(_position + 1, _commits.Count - _position - 1);
+            _commits.Add(sha);
+            _position++;
+        }
+
+        public string Back()
+        {
+            return CanGoBack ? _commits[--_position] : null;
+        }
+
+        public string Forward()
+        {
+            return CanGoForward ? _commits[++_position] : null;
+        }
+
+        public void Forget(string sha)
+        {
+            for (var i = _commits.Count - 1; i >= 0; i--)
+            {
+                if (_commits[i] != sha)
+                    continue;
+
+                _commits.RemoveAt(i);
+                if (i <= _position)
+                    _position--;
+            }
+        }
+
+        private readonly List<string> _commits = [];
+        private int _position = -1;
+    }
+}

src/Resources/Icons.axaml

@@ -1,4 +1,7 @@
 <ResourceDictionary xmlns="https://github.com/avaloniaui" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
+  <StreamGeometry x:Key="Icons.Back">M9 2L2 9L9 16L11 14L7 10H18V8H7L11 4Z</StreamGeometry>
+  <StreamGeometry x:Key="Icons.Forward">M11 2L18 9L11 16L9 14L13 10H2V8H13L9 4Z</StreamGeometry>
+  <StreamGeometry x:Key="Icons.Home">M10 1L0 10H3V19H8V13H12V19H17V10H20Z</StreamGeometry>
   <StreamGeometry x:Key="Icons.Action">M41 512c0-128 46-241 138-333C271 87 384 41 512 41s241 46 333 138c92 92 138 205 138 333s-46 241-138 333c-92 92-205 138-333 138s-241-46-333-138C87 753 41 640 41 512zm87 0c0 108 36 195 113 271s164 113 271 113c108 0 195-36 271-113s113-164 113-271-36-195-113-271c-77-77-164-113-271-113-108 0-195 36-271 113C164 317 128 404 128 512zm256 148V292l195 113L768 512l-195 113-195 113v-77zm148-113-61 36V440l61 36 61 36-61 36z</StreamGeometry>
   <StreamGeometry x:Key="Icons.Address">M306 761c3-3 8-7 16-11 15-7 35-14 60-19 4-1 14-3 11-18l-3-16c-4-18-13-14-18-13C301 699 256 724 256 763c0 58 112 91 252 91 140 0 252-33 252-91 0-38-45-64-116-78-5-1-16-3-18 13-1 6-2 11-3 15-4 18 8 18 14 19 24 5 44 11 58 18 8 4 13 8 16 11 1 2 2 2 2 1 0 3-17 15-50 24-40 12-95 19-155 19-59 0-114-7-155-19-32-9-49-21-50-24 0 0 0-0 2-2zm73-123c54 79 107 142 129 142 22 0 75-62 129-142 62-91 101-173 101-231C738 280 635 176 508 176c-127 0-230 104-230 232 0 57 39 139 101 231zm150 64a446 446 0 01-21 23c-6-6-13-14-21-23-21-25-46-57-68-91-57-84-92-159-92-204 0-102 82-184 182-184 100 0 182 82 182 184 0 45-36 120-92 204-23 33-47 66-68 91zm-21-200a102 102 0 100-204 102 102 0 000 204zm0-48a54 54 0 110-108 54 54 0 010 108z</StreamGeometry>
   <StreamGeometry x:Key="Icons.AIAssist">M304 464a128 128 0 01128-128c71 0 128 57 128 128v224a32 32 0 01-64 0V592h-128v95a32 32 0 01-64 0v-224zm64 1v64h128v-64a64 64 0 00-64-64c-35 0-64 29-64 64zM688 337c18 0 32 14 32 32v319a32 32 0 01-32 32c-18 0-32-14-32-32v-319a32 32 0 0132-32zM84 911l60-143A446 446 0 0164 512C64 265 265 64 512 64s448 201 448 448-201 448-448 448c-54 0-105-9-153-27l-242 22a32 32 0 01-32-44zm133-150-53 126 203-18 13 5c41 15 85 23 131 23 212 0 384-172 384-384S724 128 512 128 128 300 128 512c0 82 26 157 69 220l20 29z</StreamGeometry>

src/Resources/Locales/en_US.axaml

@@ -524,6 +524,9 @@
   <x:String x:Key="Text.GitLFS.TrackByExtension" xml:space="preserve">Track all *{0} files</x:String>
   <x:String x:Key="Text.GotoRevisionSelector" xml:space="preserve">Select Commit</x:String>
   <x:String x:Key="Text.Histories.AdvancedOptions" xml:space="preserve">Advanced Options</x:String>
+  <x:String x:Key="Text.Histories.NavigateBack" xml:space="preserve">Back</x:String>
+  <x:String x:Key="Text.Histories.NavigateForward" xml:space="preserve">Forward</x:String>
+  <x:String x:Key="Text.Histories.NavigateHome" xml:space="preserve">Go to current HEAD</x:String>
   <x:String x:Key="Text.Histories.Header.Author" xml:space="preserve">AUTHOR</x:String>
   <x:String x:Key="Text.Histories.Header.AuthorTime" xml:space="preserve">AUTHOR TIME</x:String>
   <x:String x:Key="Text.Histories.Header.CommitTime" xml:space="preserve">COMMIT TIME</x:String>

src/ViewModels/Histories.Navigation.cs

@@ -0,0 +1,160 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+using Avalonia.Threading;
+
+namespace SourceGit.ViewModels
+{
+    public partial class Histories
+    {
+        public bool CanNavigateBack => !_isResolvingNavigation && (_navigationHistory.CanGoBack || HasUnrecordedNavigationSelection);
+        public bool CanNavigateForward => !_isResolvingNavigation && _navigationHistory.CanGoForward;
+
+        public async Task NavigateHomeAsync()
+        {
+            CancelNavigationVisit();
+            var request = _navigationRequest;
+            // Resolve HEAD in this worktree, even if the loaded history omits it
+            // or its decorations belong to an earlier checkout.
+            var commit = await GetCommitAsync("HEAD");
+            if (request != _navigationRequest)
+                return;
+
+            if (commit == null && _commits.Count > 0)
+                commit = _commits[0];
+            if (commit != null)
+                SelectedCommits = [EnsureNavigationCommitVisible(commit)];
+        }
+
+        public Task NavigateBackAsync() => NavigateHistoryAsync(-1);
+        public Task NavigateForwardAsync() => NavigateHistoryAsync(1);
+
+        public void ResumeNavigationVisits()
+        {
+            _isNavigationActive = true;
+            ScheduleNavigationVisit();
+        }
+
+        public void SuspendNavigationVisits()
+        {
+            _isNavigationActive = false;
+            CancelNavigationVisit();
+        }
+
+        public void CancelNavigationVisit()
+        {
+            _navigationRequest++;
+            _navigationVisitTimer?.Stop();
+        }
+
+        private void ScheduleNavigationVisit()
+        {
+            CancelNavigationVisit();
+            NotifyNavigationChanged();
+            if (!_isNavigationActive || _isNavigatingHistory || _ignoreSelectionChange || _selectedCommits.Count != 1)
+                return;
+
+            if (_navigationVisitTimer == null)
+            {
+                _navigationVisitTimer = new DispatcherTimer { Interval = TimeSpan.FromSeconds(1) };
+                _navigationVisitTimer.Tick += (_, _) =>
+                {
+                    _navigationVisitTimer.Stop();
+                    if (_selectedCommits.Count == 1)
+                    {
+                        _navigationHistory.Visit(_selectedCommits[0].SHA);
+                        NotifyNavigationChanged();
+                    }
+                };
+            }
+
+            _navigationVisitTimer.Start();
+        }
+
+        private async Task NavigateHistoryAsync(int direction)
+        {
+            if (direction < 0 ? !CanNavigateBack : !CanNavigateForward)
+                return;
+
+            CancelNavigationVisit();
+            var request = _navigationRequest;
+            _isResolvingNavigation = true;
+            NotifyNavigationChanged();
+            try
+            {
+                while (true)
+                {
+                    var returnToCurrent = direction < 0 && HasUnrecordedNavigationSelection;
+                    var sha = direction < 0 ?
+                        returnToCurrent ? _navigationHistory.Current : _navigationHistory.Previous :
+                        _navigationHistory.Next;
+                    if (sha == null)
+                        return;
+
+                    var commit = _commits.Find(c => c.SHA == sha);
+                    if (commit == null)
+                    {
+                        commit = await GetCommitAsync(sha);
+                        if (request != _navigationRequest)
+                            return;
+                        if (commit == null)
+                        {
+                            // A rewritten, unreachable commit may have been pruned by Git.
+                            _navigationHistory.Forget(sha);
+                            continue;
+                        }
+                    }
+
+                    if (!returnToCurrent)
+                    {
+                        if (direction < 0)
+                            _navigationHistory.Back();
+                        else
+                            _navigationHistory.Forward();
+                    }
+
+                    _isNavigatingHistory = true;
+                    SelectedCommits = [EnsureNavigationCommitVisible(commit)];
+                    return;
+                }
+            }
+            finally
+            {
+                _isNavigatingHistory = false;
+                _isResolvingNavigation = false;
+                NotifyNavigationChanged();
+            }
+        }
+
+        private void NotifyNavigationChanged()
+        {
+            OnPropertyChanged(nameof(CanNavigateBack));
+            OnPropertyChanged(nameof(CanNavigateForward));
+        }
+
+        private Models.Commit EnsureNavigationCommitVisible(Models.Commit commit)
+        {
+            var existing = _commits.Find(c => c.SHA == commit.SHA);
+            if (existing != null)
+                return existing;
+
+            var commits = new List<Models.Commit>(_commits);
+            // Keep children above their parents when restoring an omitted row.
+            var parentIndex = commits.FindIndex(c => commit.Parents.Contains(c.SHA));
+            commits.Insert(parentIndex < 0 ? commits.Count : parentIndex, commit);
+            Commits = commits;
+            return commit;
+        }
+
+        private bool HasUnrecordedNavigationSelection => _navigationHistory.Current != null &&
+            (_selectedCommits.Count != 1 || _selectedCommits[0].SHA != _navigationHistory.Current);
+
+        private readonly Models.CommitNavigationHistory _navigationHistory = new();
+        private DispatcherTimer _navigationVisitTimer;
+        private bool _isNavigatingHistory;
+        private bool _isResolvingNavigation;
+        private bool _isNavigationActive;
+        private int _navigationRequest;
+    }
+}

src/ViewModels/Histories.cs

@@ -10,7 +10,7 @@
 
 namespace SourceGit.ViewModels
 {
-    public class Histories : ObservableObject
+    public partial class Histories : ObservableObject
     {
         public bool IsLoading
         {
@@ -526,6 +526,7 @@ private void PostCommitsChanged()
 
         private void PostSelectedCommitsChanged()
         {
+            ScheduleNavigationVisit();
             if (_ignoreSelectionChange)
                 return;
 

src/Views/Histories.axaml

@@ -272,6 +272,27 @@
             <Path Width="12" Height="12"
                   Data="{StaticResource Icons.Settings2}"/>
           </Button>
+          <Button x:Name="NavigationHomeButton" Classes="icon_button" Width="18" Height="18" Focusable="False"
+                  Command="{Binding NavigateHomeAsync}">
+            <ToolTip.Tip>
+              <TextBlock><Run Text="{DynamicResource Text.Histories.NavigateHome}"/><Run Text=" (Alt+Home)"/></TextBlock>
+            </ToolTip.Tip>
+            <Path Width="14" Height="14" Data="{StaticResource Icons.Home}"/>
+          </Button>
+          <Button x:Name="NavigationBackButton" Classes="icon_button" Width="18" Height="18" Focusable="False"
+                  Command="{Binding NavigateBackAsync}" IsEnabled="{Binding CanNavigateBack}">
+            <ToolTip.Tip>
+              <TextBlock><Run Text="{DynamicResource Text.Histories.NavigateBack}"/><Run Text="{OnPlatform ' (Alt+Left)', macOS=' (⌘+[)'}"/></TextBlock>
+            </ToolTip.Tip>
+            <Path Width="14" Height="14" Data="{StaticResource Icons.Back}"/>
+          </Button>
+          <Button x:Name="NavigationForwardButton" Classes="icon_button" Width="18" Height="18" Focusable="False"
+                  Command="{Binding NavigateForwardAsync}" IsEnabled="{Binding CanNavigateForward}">
+            <ToolTip.Tip>
+              <TextBlock><Run Text="{DynamicResource Text.Histories.NavigateForward}"/><Run Text="{OnPlatform ' (Alt+Right)', macOS=' (⌘+])'}"/></TextBlock>
+            </ToolTip.Tip>
+            <Path Width="14" Height="14" Data="{StaticResource Icons.Forward}"/>
+          </Button>
         </StackPanel>
       </Border>
 

src/Views/Histories.axaml.cs

@@ -137,12 +137,9 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
 
             if (change.Property == SelectedCommitsProperty && IsLoaded && !_ignoreSelectionChanged)
             {
-                if (change.OldValue is List<Models.Commit> { Count: 1 } old &&
-                    change.NewValue is List<Models.Commit> { Count: 1 } cur &&
-                    old[0] == cur[0])
-                    ScrollIntoView(old[0], null);
-                else
-                    ApplySelection();
+                ApplySelection();
+                if (change.NewValue is List<Models.Commit> { Count: 1 } selected)
+                    ScrollIntoView(selected[0], null);
             }
         }
 
@@ -372,6 +369,32 @@ public bool IsDetailsPanelExpanded
         public Histories()
         {
             InitializeComponent();
+            AddHandler(KeyDownEvent, OnNavigationKeyDown, RoutingStrategies.Tunnel);
+            Loaded += (_, _) => (DataContext as ViewModels.Histories)?.ResumeNavigationVisits();
+            Unloaded += (_, _) => (DataContext as ViewModels.Histories)?.SuspendNavigationVisits();
+        }
+
+        private async void OnNavigationKeyDown(object sender, KeyEventArgs e)
+        {
+            if (DataContext is not ViewModels.Histories vm)
+                return;
+
+            var macCommand = OperatingSystem.IsMacOS() && e.KeyModifiers == KeyModifiers.Meta;
+            if (e.KeyModifiers == KeyModifiers.Alt && e.Key == Key.Home)
+            {
+                e.Handled = true;
+                await vm.NavigateHomeAsync();
+            }
+            else if ((e.KeyModifiers == KeyModifiers.Alt && e.Key == Key.Left) || (macCommand && e.Key == Key.OemOpenBrackets))
+            {
+                e.Handled = true;
+                await vm.NavigateBackAsync();
+            }
+            else if ((e.KeyModifiers == KeyModifiers.Alt && e.Key == Key.Right) || (macCommand && e.Key == Key.OemCloseBrackets))
+            {
+                e.Handled = true;
+                await vm.NavigateForwardAsync();
+            }
         }
 
         public async Task GotoParent()
@@ -462,8 +485,13 @@ public async Task GotoChild()
 
         protected override void OnDataContextChanged(EventArgs e)
         {
+            _navigationHistories?.SuspendNavigationVisits();
             base.OnDataContextChanged(e);
 
+            _navigationHistories = DataContext as ViewModels.Histories;
+            if (IsLoaded)
+                _navigationHistories?.ResumeNavigationVisits();
+
             if (DataContext is ViewModels.Histories vm)
                 CommitListContainer.Columns[1].Width = new(vm.AuthorColumnWidth, DataGridLengthUnitType.Pixel);
         }
@@ -1964,6 +1992,7 @@ private async Task InteractiveRebaseWithPrefillActionAsync(ViewModels.Repository
                 await this.ShowDialogAsync(new ViewModels.InteractiveRebase(repo, on, prefill));
         }
 
+        private ViewModels.Histories _navigationHistories = null;
         private Models.Branch _currentBranch = null;
         private Models.Bisect _bisect = null;
         private bool _hasSingleRemote = false;

tests/HistoryNavigationChecks/HistoryNavigationChecks.csproj

@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+  <ItemGroup>
+    <ProjectReference Include="../../src/SourceGit.csproj" />
+    <PackageReference Include="Avalonia.Headless" Version="11.3.22" />
+  </ItemGroup>
+</Project>