Batch 8: Blacklist + FileTree + resource management (#376)

- Add Cancel() to GeneralUpdateBootstrap with CancellationTokenSource
- Wire CancellationToken through LaunchWithStrategy with finally cleanup
- Create FileTreeEnumerator: recursive file enumeration with
  blacklist filtering via IBlackListMatcher

Closes #375

Author: JusterZhu

src/c#/GeneralUpdate.Core/Bootstrap/GeneralUpdateBootstrap.cs

@@ -4,6 +4,7 @@
 using System.IO;
 using System.Linq;
 using System.Runtime.InteropServices;
+using System.Threading;
 using System.Text;
 using System.Text.Json;
 using System.Threading.Tasks;
@@ -37,12 +38,20 @@ public class GeneralUpdateBootstrap : AbstractBootstrap<GeneralUpdateBootstrap,
     private Func<bool>? _customSkipOption;
     private Func<UpdateInfoEventArgs, bool>? _updatePrecheck;
     private readonly List<Func<bool>> _customOptions = new();
+    private CancellationTokenSource? _cts;
 
     public GeneralUpdateBootstrap()
     {
         InitializeFromEnvironment();
     }
 
+    /// <summary>Cancel the current update operation.</summary>
+    public void Cancel()
+    {
+        _cts?.Cancel();
+        GeneralTracer.Info("GeneralUpdateBootstrap: cancellation requested.");
+    }
+
     // ════════════════════════════════════════════════════════════════
     // Launch — AppType dispatch via role strategies
     // ════════════════════════════════════════════════════════════════
@@ -69,8 +78,11 @@ public override async Task<GeneralUpdateBootstrap> LaunchAsync()
 
     private async Task<GeneralUpdateBootstrap> LaunchWithStrategy(IStrategy roleStrategy)
     {
+        _cts = new CancellationTokenSource();
+        var token = _cts.Token;
         try
         {
+            token.ThrowIfCancellationRequested();
             ApplyRuntimeOptions();
 
             // Resolve hooks and reporter from extensions
@@ -107,6 +119,11 @@ private async Task<GeneralUpdateBootstrap> LaunchWithStrategy(IStrategy roleStra
             GeneralTracer.Error("LaunchWithStrategy failed.", ex);
             EventManager.Instance.Dispatch(this, new ExceptionEventArgs(ex, ex.Message));
         }
+        finally
+        {
+            _cts?.Dispose();
+            _cts = null;
+        }
         return this;
     }
 

src/c#/GeneralUpdate.Core/FileSystem/FileTreeEnumerator.cs

@@ -0,0 +1,53 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using GeneralUpdate.Core.Configuration;
+
+namespace GeneralUpdate.Core.FileSystem;
+
+/// <summary>
+/// Recursively enumerates files in a directory,
+/// applying blacklist filtering via IBlackListMatcher.
+/// </summary>
+public class FileTreeEnumerator
+{
+    private readonly IBlackListMatcher _matcher;
+
+    public FileTreeEnumerator(IBlackListMatcher matcher)
+    {
+        _matcher = matcher ?? throw new ArgumentNullException(nameof(matcher));
+    }
+
+    /// <summary>
+    /// Enumerate all files under <paramref name="rootPath"/>,
+    /// skipping blacklisted files and directories.
+    /// </summary>
+    public IEnumerable<string> EnumerateFiles(string rootPath)
+    {
+        if (!Directory.Exists(rootPath))
+            yield break;
+
+        foreach (var filePath in Directory.EnumerateFiles(rootPath))
+        {
+            var relativePath = Path.GetFileName(filePath);
+            if (!_matcher.IsBlacklisted(relativePath))
+                yield return filePath;
+        }
+
+        foreach (var dirPath in Directory.EnumerateDirectories(rootPath))
+        {
+            var dirName = Path.GetFileName(dirPath);
+            if (_matcher.ShouldSkipDirectory(dirName))
+                continue;
+
+            foreach (var file in EnumerateFiles(dirPath))
+                yield return file;
+        }
+    }
+
+    /// <summary>
+    /// Create an enumerator from a BlackListConfig.
+    /// </summary>
+    public static FileTreeEnumerator FromConfig(BlackListConfig config)
+        => new(new DefaultBlackListMatcher(config));
+}