Show last commit and build date in About

SPEC.md

@@ -779,7 +779,7 @@ Behaviour:
 - **Diff viewer** selects the built-in viewer, a detected external program, or an executable chosen by the user.
 - **Keyboard shortcut...** opens the shortcut recorder without changing the active shortcut unless Save succeeds.
 - **Start at login** toggles per-user startup registration (section 24).
-- **About ClipDiff** opens a reusable native window showing the application icon, the product version and short source commit hash, Stuart Dunkeld, `stuartd.dev`, and the source repository link.
+- **About ClipDiff** opens a reusable native window showing the application icon, the last source commit (short hash) and build date/time in UTC (embedded at build time), without a product version, Stuart Dunkeld, `stuartd.dev`, and the source repository link.
 - **Quit ClipDiff** removes the tray icon, unregisters native listeners/hotkeys, clears references to captured text, and shuts down.
 - Double-clicking the tray icon may invoke **Show Diff** when available.
 - The ordinary native right-click context-menu behaviour is sufficient.

src/ClipDiff.Windows/ClipDiff.Windows.csproj

@@ -11,6 +11,13 @@
     <ApplicationManifest>app.manifest</ApplicationManifest>
     <ApplicationIcon>Assets/ClipDiff.ico</ApplicationIcon>
   </PropertyGroup>
+  <PropertyGroup>
+    <!-- Override BuildDateUtc for reproducible builds; otherwise stamp this build in UTC. -->
+    <BuildDateUtc Condition="'$(BuildDateUtc)' == ''">$([System.DateTime]::UtcNow.ToString("O"))</BuildDateUtc>
+  </PropertyGroup>
+  <ItemGroup>
+    <AssemblyMetadata Include="BuildDateUtc" Value="$(BuildDateUtc)" />
+  </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="../ClipDiff.Core/ClipDiff.Core.csproj" />
   </ItemGroup>

src/ClipDiff.Windows/Views/AboutBuildInfoFormatter.cs

@@ -0,0 +1,29 @@
+using System.Globalization;
+
+namespace ClipDiff.Windows.Views;
+
+internal static class AboutBuildInfoFormatter
+{
+	private const int ShortCommitLength = 7;
+
+	public static string Format(string? informationalVersion, string? buildDateUtc)
+	{
+		var parts = informationalVersion?.Split('+', 2);
+		var commit = parts is { Length: 2 }
+			? parts[1].Split('.').LastOrDefault(IsCommitHash)
+			: null;
+		var shortCommit = commit is null ? "Unknown" : commit[..ShortCommitLength];
+		var buildDate = DateTimeOffset.TryParse(buildDateUtc, CultureInfo.InvariantCulture,
+			DateTimeStyles.AssumeUniversal, out var timestamp)
+			? timestamp.UtcDateTime.ToString("yyyy-MM-dd HH:mm 'UTC'", CultureInfo.InvariantCulture)
+			: "Unknown";
+
+		return $"Last commit: {shortCommit}\nBuild date: {buildDate}";
+	}
+
+	private static bool IsCommitHash(string value) =>
+		value.Length >= ShortCommitLength && value.All(IsHexDigit);
+
+	private static bool IsHexDigit(char value) =>
+		value is >= '0' and <= '9' or >= 'a' and <= 'f' or >= 'A' and <= 'F';
+}

src/ClipDiff.Windows/Views/AboutWindow.xaml

@@ -55,9 +55,10 @@
 
         <StackPanel Grid.Row="0" Grid.Column="1">
             <TextBlock Text="ClipDiff" FontSize="26" FontWeight="SemiBold" />
-            <TextBlock x:Name="VersionText"
+            <TextBlock x:Name="BuildInfoText"
                        Margin="0,2,0,16"
-                       Opacity="0.72" />
+                       Opacity="0.72"
+                       TextWrapping="Wrap" />
             <TextBlock Text="A minimal clipboard comparison tool."
                        Margin="0,0,0,16"
                        TextWrapping="Wrap" />

src/ClipDiff.Windows/Views/AboutWindow.xaml.cs

@@ -10,69 +10,72 @@ namespace ClipDiff.Windows.Views;
 
 public partial class AboutWindow : Window
 {
-    public AboutWindow()
-    {
-        InitializeComponent();
-        VersionText.Text = $"Version {GetDisplayVersion()}";
-    }
+	public AboutWindow()
+	{
+		InitializeComponent();
+		BuildInfoText.Text = GetBuildInfo();
+	}
 
-    public bool AllowClose { get; set; }
+	public bool AllowClose { get; set; }
 
-    private void OnSourceInitialized(object? sender, EventArgs args)
-    {
-        var windowHandle = new WindowInteropHelper(this).Handle;
-        var enabled = 1;
-        var result = NativeMethods.DwmSetWindowAttribute(
-            windowHandle,
-            NativeMethods.DwmwaUseImmersiveDarkMode,
-            ref enabled,
-            sizeof(int));
+	private void OnSourceInitialized(object? sender, EventArgs args)
+	{
+		var windowHandle = new WindowInteropHelper(this).Handle;
+		var enabled = 1;
+		var result = NativeMethods.DwmSetWindowAttribute(
+			windowHandle,
+			NativeMethods.DwmwaUseImmersiveDarkMode,
+			ref enabled,
+			sizeof(int));
 
-        if (result != 0)
-        {
-            NativeMethods.DwmSetWindowAttribute(
-                windowHandle,
-                NativeMethods.DwmwaUseImmersiveDarkModeBefore20H1,
-                ref enabled,
-                sizeof(int));
-        }
-    }
+		if (result != 0)
+		{
+			NativeMethods.DwmSetWindowAttribute(
+				windowHandle,
+				NativeMethods.DwmwaUseImmersiveDarkModeBefore20H1,
+				ref enabled,
+				sizeof(int));
+		}
+	}
 
-    private static string GetDisplayVersion()
-    {
-        var assembly = typeof(AboutWindow).Assembly;
-
-        var informationalVersion = assembly
-            .GetCustomAttribute<AssemblyInformationalVersionAttribute>()?
-            .InformationalVersion;
+	private static string GetBuildInfo()
+	{
+		var assembly = typeof(AboutWindow).Assembly;
 
-        return AboutVersionFormatter.Format(informationalVersion, assembly.GetName().Version);
-    }
+		var informationalVersion = assembly
+			.GetCustomAttribute<AssemblyInformationalVersionAttribute>()?
+			.InformationalVersion;
 
-    private void OnLinkRequestNavigate(object sender, RequestNavigateEventArgs args)
-    {
-        try
-        {
-            Process.Start(new ProcessStartInfo(args.Uri.AbsoluteUri) { UseShellExecute = true });
-        }
-        catch (Exception exception) when (exception is Win32Exception or InvalidOperationException or NotSupportedException)
-        {
-            System.Media.SystemSounds.Beep.Play();
-        }
+		var buildDate = assembly.GetCustomAttributes<AssemblyMetadataAttribute>()
+			.FirstOrDefault(attribute => attribute.Key == "BuildDateUtc")?.Value;
 
-        args.Handled = true;
-    }
+		return AboutBuildInfoFormatter.Format(informationalVersion, buildDate);
+	}
 
-    private void OnCloseClick(object sender, RoutedEventArgs args) => Hide();
+	private void OnLinkRequestNavigate(object sender, RequestNavigateEventArgs args)
+	{
+		try
+		{
+			Process.Start(new ProcessStartInfo(args.Uri.AbsoluteUri) { UseShellExecute = true });
+		}
+		catch (Exception exception) when (exception is Win32Exception or InvalidOperationException or NotSupportedException)
+		{
+			System.Media.SystemSounds.Beep.Play();
+		}
 
-    private void OnClosing(object? sender, CancelEventArgs args)
-    {
-        if (AllowClose)
-        {
-            return;
-        }
+		args.Handled = true;
+	}
 
-        args.Cancel = true;
-        Hide();
-    }
+	private void OnCloseClick(object sender, RoutedEventArgs args) => Hide();
+
+	private void OnClosing(object? sender, CancelEventArgs args)
+	{
+		if (AllowClose)
+		{
+			return;
+		}
+
+		args.Cancel = true;
+		Hide();
+	}
 }

tests/ClipDiff.Windows.Tests/AboutBuildInfoFormatterTests.cs

@@ -0,0 +1,60 @@
+using ClipDiff.Windows.Views;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace ClipDiff.Windows.Tests;
+
+[TestClass]
+public sealed class AboutBuildInfoFormatterTests
+{
+	[TestMethod]
+	[DataRow("1.0+753aab75f36e959cf8dfa6d72a2175110c9ed608")]
+	[DataRow("2.3.4-preview.1+local.753aab75f36e959cf8dfa6d72a2175110c9ed608")]
+	public void ShowsCommitAndBuildDateWithoutVersion(string informationalVersion)
+	{
+		var result = AboutBuildInfoFormatter.Format(informationalVersion, "2026-10-19T10:43:44.0000000Z");
+
+		Assert.AreEqual("Last commit: 753aab7\nBuild date: 2026-10-19 10:43 UTC", result);
+	}
+
+	[TestMethod]
+	[DataRow(null)]
+	[DataRow("1.0")]
+	[DataRow("1.0+preview")]
+	public void MissingCommitIsExplicit(string? informationalVersion)
+	{
+		var result = AboutBuildInfoFormatter.Format(informationalVersion, "2026-10-19T10:43:44Z");
+
+		Assert.AreEqual("Last commit: Unknown\nBuild date: 2026-10-19 10:43 UTC", result);
+	}
+
+	[TestMethod]
+	[DataRow(null)]
+	[DataRow("")]
+	[DataRow("invalid")]
+	public void MissingOrInvalidBuildDateIsExplicit(string? buildDate)
+	{
+		var result = AboutBuildInfoFormatter.Format("1.0+753aab75f36e959cf8dfa6d72a2175110c9ed608", buildDate);
+
+		Assert.AreEqual("Last commit: 753aab7\nBuild date: Unknown", result);
+	}
+
+	[TestMethod]
+	public void NormalizesBuildDateToUtc()
+	{
+		var result = AboutBuildInfoFormatter.Format(null, "2026-10-19T11:43:44+01:00");
+
+		Assert.AreEqual("Last commit: Unknown\nBuild date: 2026-10-19 10:43 UTC", result);
+	}
+
+	[TestMethod]
+	public void BuildContainsTimestampMetadata()
+	{
+		var metadata = typeof(AboutBuildInfoFormatter).Assembly
+			.GetCustomAttributes(typeof(System.Reflection.AssemblyMetadataAttribute), false)
+			.Cast<System.Reflection.AssemblyMetadataAttribute>()
+			.Single(attribute => attribute.Key == "BuildDateUtc");
+
+		Assert.IsTrue(DateTimeOffset.TryParse(metadata.Value, System.Globalization.CultureInfo.InvariantCulture,
+			System.Globalization.DateTimeStyles.AssumeUniversal, out _));
+	}
+}