Address Copilot review feedback

- Fix typo (its -> it's) in DumpArchive comment
- Document that filtered dumps omit External References (command-dump.md, textdumper.md)
- Add tests: type-filter omits External References, --stdout/-o mutual exclusion error,
  multi-SerializedFile archive refusal (data.unity3d)
- Assert no .txt file is written by --stdout in DumpText_Stdout_WritesDumpToStdout

Author: SkowronskiAndrew

Documentation/command-dump.md

@@ -145,7 +145,7 @@ UnityDataTool dump /path/to/file.bundle --typetree-data /path/to/typetree.bin
 
 ## Output Format
 
-The output is similar to Unity's `binary2text` tool. Each file begins with external references:
+The output is similar to Unity's `binary2text` tool. Unfiltered dumps begin with external references (when filtering with `-i` or `-t` this section is omitted — use the [`serialized-file externalrefs`](#) command if you want them separately):
 
 ```
 External References

Documentation/textdumper.md

@@ -15,7 +15,7 @@ There will be one output file per SerializedFile. Depending on the type of the i
 be more than one output file (e.g. AssetBundles are archives that can contain several
 SerializedFiles).
 
-The first lines of the output file looks like this:
+For an unfiltered dump, the first lines of the output file look like this (when `ObjectId` or `TypeFilter` are set the External References section is omitted, and the output starts directly with the matching object entries):
 
     External References
     path(1): "Library/unity default resources" GUID: 0000000000000000e000000000000000 Type: 0

TextDumper/TextDumperTool.cs

@@ -99,7 +99,7 @@ int DumpSerializedFile(DumpOptions options)
     }
 
     // For convenience we also support directly dumping serialized files that are inside an archive,
-    // so that its not necessary to use `archive extract` if you only want to see values from the object serialization.
+    // so that it's not necessary to use `archive extract` if you only want to see values from the object serialization.
     int DumpArchive(DumpOptions options)
     {
         using var archive = UnityFileSystem.MountArchive(options.Path, "/");

UnityDataTool.Tests/DumpTests.cs

@@ -12,13 +12,15 @@ public class DumpTests
     private string m_TestDataFolder;
     private string m_SerializedFilePath;
     private string m_ResourceFilePath;
+    private string m_MultiSerializedFileArchivePath;
 
     [OneTimeSetUp]
     public void OneTimeSetup()
     {
         m_TestDataFolder = Path.Combine(TestContext.CurrentContext.TestDirectory, "Data");
         m_SerializedFilePath = Path.Combine(m_TestDataFolder, "PlayerWithTypeTrees", "level0");
         m_ResourceFilePath = Path.Combine(m_TestDataFolder, "PlayerWithTypeTrees", "sharedassets0.assets.resS");
+        m_MultiSerializedFileArchivePath = Path.Combine(m_TestDataFolder, "PlayerDataCompressed", "data.unity3d");
     }
 
     [Test]
@@ -99,6 +101,72 @@ public async Task Dump_Stdout_FilterByObjectId_DoesNotIncludeExternalReferences(
         Assert.That(output, Does.Not.Contain("External References"));
     }
 
+    [Test]
+    public async Task Dump_Stdout_FilterByType_DoesNotIncludeExternalReferences()
+    {
+        using var sw = new StringWriter();
+        var currentOut = Console.Out;
+        try
+        {
+            Console.SetOut(sw);
+            Assert.AreEqual(0, await Program.Main(new string[] { "dump", m_SerializedFilePath, "--stdout", "-t", "RenderSettings" }));
+        }
+        finally
+        {
+            Console.SetOut(currentOut);
+        }
+
+        var output = sw.ToString();
+        Assert.That(output, Does.Contain("(ClassID: 104)"));
+        Assert.That(output, Does.Not.Contain("External References"));
+    }
+
+    [Test]
+    public async Task Dump_Stdout_WithOutputPath_ReturnsError()
+    {
+        using var swOut = new StringWriter();
+        using var swErr = new StringWriter();
+        var currentOut = Console.Out;
+        var currentErr = Console.Error;
+        try
+        {
+            Console.SetOut(swOut);
+            Console.SetError(swErr);
+            Assert.AreNotEqual(0, await Program.Main(new string[] { "dump", m_SerializedFilePath, "--stdout", "-o", m_TestDataFolder }));
+        }
+        finally
+        {
+            Console.SetOut(currentOut);
+            Console.SetError(currentErr);
+        }
+
+        Assert.That(swErr.ToString(), Does.Contain("--stdout and -o/--output-path are mutually exclusive."));
+    }
+
+    [Test]
+    public async Task Dump_Stdout_MultipleSerializedFilesArchive_Refused()
+    {
+        using var swOut = new StringWriter();
+        using var swErr = new StringWriter();
+        var currentOut = Console.Out;
+        var currentErr = Console.Error;
+        try
+        {
+            Console.SetOut(swOut);
+            Console.SetError(swErr);
+            Assert.AreNotEqual(0, await Program.Main(new string[] { "dump", m_MultiSerializedFileArchivePath, "--stdout", "-t", "MonoBehaviour" }));
+        }
+        finally
+        {
+            Console.SetOut(currentOut);
+            Console.SetError(currentErr);
+        }
+
+        var err = swErr.ToString();
+        Assert.That(err, Does.Contain("--stdout cannot be used with an archive containing multiple SerializedFiles"));
+        Assert.That(err, Does.Contain("(5 found)"));
+    }
+
     [Test]
     public async Task Dump_Stdout_FilterByObjectId_NotFound_PrintsNotFoundMessage()
     {

UnityDataTool.Tests/UnityDataToolAssetBundleTests.cs

@@ -152,6 +152,7 @@ public async Task DumpText_SkipLargeArrays_TextFileCreatedCorrectly(
     public async Task DumpText_Stdout_WritesDumpToStdout()
     {
         var path = Path.Combine(Context.UnityDataFolder, "assetbundle");
+        var unwantedOutputFile = Path.Combine(m_TestOutputFolder, "CAB-5d40f7cad7c871cf2ad2af19ac542994.txt");
 
         using var sw = new StringWriter();
         var currentOut = Console.Out;
@@ -165,6 +166,8 @@ public async Task DumpText_Stdout_WritesDumpToStdout()
             Console.SetOut(currentOut);
         }
 
+        Assert.IsFalse(File.Exists(unwantedOutputFile), "--stdout should not also write a .txt file");
+
         var content = sw.ToString();
         var expected = File.ReadAllText(Path.Combine(Context.ExpectedDataFolder, "dump", "CAB-5d40f7cad7c871cf2ad2af19ac542994.txt"));