Add Directory.Copy extension method

Directory.Packages.props

@@ -10,7 +10,7 @@
     <PackageVersion Include="FluentAssertions" Version="8.9.0" />
     <PackageVersion Include="Gress" Version="2.1.1" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.4.0" />
-    <PackageVersion Include="PolyShim" Version="2.9.0" />
+    <PackageVersion Include="PolyShim" Version="2.10.0" />
     <PackageVersion Include="xunit" Version="2.9.3" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="3.1.5" />
     <PackageVersion Include="Xunit.SkippableFact" Version="1.5.61" />

PowerKit.Tests/DirectoryExtensionsTests.cs

@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.Runtime.Versioning;
 using FluentAssertions;
 using PowerKit;
 using PowerKit.Extensions;
@@ -9,6 +10,124 @@ namespace PowerKit.Tests;
 
 public class DirectoryExtensionsTests
 {
+    [Fact]
+    public void Copy_Test()
+    {
+        // Arrange
+        using var sourceDirectory = TempDirectory.Create();
+        using var destinationDirectory = TempDirectory.Create();
+
+        File.WriteAllText(Path.Combine(sourceDirectory.Path, "file.txt"), "hello");
+
+        // Act
+        Directory.Copy(sourceDirectory.Path, destinationDirectory.Path);
+
+        // Assert
+        File.ReadAllText(Path.Combine(destinationDirectory.Path, "file.txt")).Should().Be("hello");
+    }
+
+    [Fact]
+    public void Copy_Nested_Test()
+    {
+        // Arrange
+        using var sourceDirectory = TempDirectory.Create();
+        using var destinationDirectory = TempDirectory.Create();
+
+        Directory.CreateDirectory(Path.Combine(sourceDirectory.Path, "sub"));
+        File.WriteAllText(Path.Combine(sourceDirectory.Path, "sub", "file.txt"), "nested");
+
+        // Act
+        Directory.Copy(sourceDirectory.Path, destinationDirectory.Path);
+
+        // Assert
+        File.ReadAllText(Path.Combine(destinationDirectory.Path, "sub", "file.txt"))
+            .Should()
+            .Be("nested");
+    }
+
+    [Fact]
+    public void Copy_Overwrite_Test()
+    {
+        // Arrange
+        using var sourceDirectory = TempDirectory.Create();
+        using var destinationDirectory = TempDirectory.Create();
+
+        File.WriteAllText(Path.Combine(sourceDirectory.Path, "file.txt"), "new");
+        File.WriteAllText(Path.Combine(destinationDirectory.Path, "file.txt"), "old");
+
+        // Act
+        Directory.Copy(sourceDirectory.Path, destinationDirectory.Path, true);
+
+        // Assert
+        File.ReadAllText(Path.Combine(destinationDirectory.Path, "file.txt")).Should().Be("new");
+    }
+
+    [Fact]
+    public void Copy_NoOverwrite_Test()
+    {
+        // Arrange
+        using var sourceDirectory = TempDirectory.Create();
+        using var destinationDirectory = TempDirectory.Create();
+
+        File.WriteAllText(Path.Combine(sourceDirectory.Path, "file.txt"), "source");
+        File.WriteAllText(Path.Combine(destinationDirectory.Path, "file.txt"), "existing");
+
+        // Act
+        var act = () => Directory.Copy(sourceDirectory.Path, destinationDirectory.Path, false);
+
+        // Assert
+        act.Should().Throw<IOException>();
+    }
+
+    [Fact]
+    public void Copy_Truncates_Test()
+    {
+        // Arrange
+        using var sourceDirectory = TempDirectory.Create();
+        using var destinationDirectory = TempDirectory.Create();
+
+        File.WriteAllText(Path.Combine(sourceDirectory.Path, "file.txt"), "hi");
+        File.WriteAllText(Path.Combine(destinationDirectory.Path, "file.txt"), "longer content");
+
+        // Act
+        Directory.Copy(sourceDirectory.Path, destinationDirectory.Path, true);
+
+        // Assert
+        File.ReadAllText(Path.Combine(destinationDirectory.Path, "file.txt")).Should().Be("hi");
+    }
+
+    [SkippableFact]
+    [UnsupportedOSPlatform("windows")]
+    public void Copy_UnixFileMode_Test()
+    {
+        Skip.If(OperatingSystem.IsWindows());
+
+        // Arrange
+        using var sourceDirectory = TempDirectory.Create();
+        using var destinationDirectory = TempDirectory.Create();
+
+        var sourceFilePath = Path.Combine(sourceDirectory.Path, "file.sh");
+        File.WriteAllText(sourceFilePath, "#!/bin/sh");
+        File.SetUnixFileMode(
+            sourceFilePath,
+            UnixFileMode.UserRead
+                | UnixFileMode.UserWrite
+                | UnixFileMode.UserExecute
+                | UnixFileMode.GroupRead
+                | UnixFileMode.GroupExecute
+                | UnixFileMode.OtherRead
+                | UnixFileMode.OtherExecute
+        );
+
+        // Act
+        Directory.Copy(sourceDirectory.Path, destinationDirectory.Path);
+
+        // Assert
+        File.GetUnixFileMode(Path.Combine(destinationDirectory.Path, "file.sh"))
+            .Should()
+            .Be(File.GetUnixFileMode(sourceFilePath));
+    }
+
     [Fact]
     public void CheckWriteAccess_Test()
     {

PowerKit/Extensions/DirectoryExtensions.cs

@@ -1,7 +1,9 @@
 #nullable enable
 using System;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
+using System.Linq;
 
 namespace PowerKit.Extensions;
 
@@ -43,6 +45,94 @@ public static bool TryDelete(string path, bool recursive = false)
             }
         }
 
+        /// <summary>
+        /// Recursively copies all files from <paramref name="sourcePath" /> to <paramref name="destinationPath" />.
+        /// Destination files are opened with exclusive locks before any data is written.
+        /// Concurrent readers may be blocked or fail with a sharing violation while a file is being updated,
+        /// and this method does not guarantee atomic old-or-new visibility to readers.
+        /// </summary>
+        public static void Copy(string sourcePath, string destinationPath, bool overwrite = true)
+        {
+            var sourceStreams = new List<FileStream>();
+            var destinationStreams = new List<FileStream>();
+
+            try
+            {
+                // Create all destination directories
+                Directory.CreateDirectory(destinationPath);
+                foreach (
+                    var sourceDirectoryPath in Directory.GetDirectories(
+                        sourcePath,
+                        "*",
+                        SearchOption.AllDirectories
+                    )
+                )
+                {
+                    Directory.CreateDirectory(
+                        Path.Combine(
+                            destinationPath,
+                            Path.GetRelativePath(sourcePath, sourceDirectoryPath)
+                        )
+                    );
+                }
+
+                // Create file stream pairs
+                foreach (
+                    var sourceFilePath in Directory.GetFiles(
+                        sourcePath,
+                        "*",
+                        SearchOption.AllDirectories
+                    )
+                )
+                {
+                    sourceStreams.Add(File.OpenRead(sourceFilePath));
+
+                    var destinationFilePath = Path.Combine(
+                        destinationPath,
+                        Path.GetRelativePath(sourcePath, sourceFilePath)
+                    );
+
+                    destinationStreams.Add(
+                        overwrite
+                            ? File.OpenWrite(destinationFilePath)
+                            : File.Open(
+                                destinationFilePath,
+                                FileMode.CreateNew,
+                                FileAccess.Write,
+                                FileShare.None
+                            )
+                    );
+                }
+
+                // Copy the file contents
+                foreach (
+                    var (sourceStream, destinationStream) in sourceStreams.Zip(
+                        destinationStreams,
+                        (s, d) => (s, d)
+                    )
+                )
+                {
+                    sourceStream.CopyTo(destinationStream);
+
+                    // Truncate the destination file if the source file is shorter
+                    destinationStream.SetLength(sourceStream.Length);
+
+                    // Preserve Unix file permissions on non-Windows platforms
+                    if (!OperatingSystem.IsWindows())
+                    {
+                        File.SetUnixFileMode(
+                            destinationStream.Name,
+                            File.GetUnixFileMode(sourceStream.Name)
+                        );
+                    }
+                }
+            }
+            finally
+            {
+                Disposable.Merge([.. sourceStreams, .. destinationStreams]).Dispose();
+            }
+        }
+
         /// <summary>
         /// Checks if it's possible to write to the specified directory.
         /// </summary>