Optimize cross-filesystem operations

Adds a new  function to  that resolves a path
through all underlying filesystems. Allows cross-file system operations
to resolve to the final FS and call operations directly on that file system.

src/Zio.Tests/FileSystems/TestMemoryFileSystem.cs

@@ -1,5 +1,5 @@
 // Copyright (c) Alexandre Mutel. All rights reserved.
-// This file is licensed under the BSD-Clause 2 license. 
+// This file is licensed under the BSD-Clause 2 license.
 // See the license.txt file in the project root for more information.
 
 using Zio.FileSystems;
@@ -36,10 +36,10 @@ public void TestCopyFileSystemSubFolder()
         fs.CopyTo(dest, subFolder, true);
 
         var destSubFileSystem = dest.GetOrCreateSubFileSystem(subFolder);
-        
+
         AssertFileSystemEqual(fs, destSubFileSystem);
     }
-    
+
 
     [Fact]
     public void TestWatcher()
@@ -80,4 +80,57 @@ public void TestDispose()
         memfs.Dispose();
         Assert.Throws<ObjectDisposedException>(() => memfs.DirectoryExists("/"));
     }
+
+    [Fact]
+    public void TestCopyFileCross()
+    {
+        var fs = new TriggerMemoryFileSystem();
+        fs.CreateDirectory("/sub1");
+        fs.CreateDirectory("/sub2");
+        var sub1 = new SubFileSystem(fs, "/sub1");
+        var sub2 = new SubFileSystem(fs, "/sub2");
+        sub1.WriteAllText("/file.txt", "test");
+        sub1.CopyFileCross("/file.txt", sub2, "/file.txt", overwrite: false);
+        Assert.Equal("test", sub2.ReadAllText("/file.txt"));
+        Assert.Equal(TriggerMemoryFileSystem.TriggerType.Copy, fs.Triggered);
+    }
+
+    [Fact]
+    public void TestMoveFileCross()
+    {
+        var fs = new TriggerMemoryFileSystem();
+        fs.CreateDirectory("/sub1");
+        fs.CreateDirectory("/sub2");
+        var sub1 = new SubFileSystem(fs, "/sub1");
+        var sub2 = new SubFileSystem(fs, "/sub2");
+        sub1.WriteAllText("/file.txt", "test");
+        sub1.MoveFileCross("/file.txt", sub2, "/file.txt");
+        Assert.Equal("test", sub2.ReadAllText("/file.txt"));
+        Assert.False(sub1.FileExists("/file.txt"));
+        Assert.Equal(TriggerMemoryFileSystem.TriggerType.Move, fs.Triggered);
+    }
+
+    private sealed class TriggerMemoryFileSystem : MemoryFileSystem
+    {
+        public enum TriggerType
+        {
+            None,
+            Copy,
+            Move
+        }
+
+        public TriggerType Triggered { get; private set; } = TriggerType.None;
+
+        protected override void CopyFileImpl(UPath srcPath, UPath destPath, bool overwrite)
+        {
+            Triggered = TriggerType.Copy;
+            base.CopyFileImpl(srcPath, destPath, overwrite);
+        }
+
+        protected override void MoveFileImpl(UPath srcPath, UPath destPath)
+        {
+            Triggered = TriggerType.Move;
+            base.MoveFileImpl(srcPath, destPath);
+        }
+    }
 }

src/Zio.Tests/FileSystems/TestPhysicalFileSystem.cs

@@ -1,5 +1,5 @@
 // Copyright (c) Alexandre Mutel. All rights reserved.
-// This file is licensed under the BSD-Clause 2 license. 
+// This file is licensed under the BSD-Clause 2 license.
 // See the license.txt file in the project root for more information.
 
 using System.IO;
@@ -352,7 +352,7 @@ public void TestEnumerate()
         var expectedPaths = Directory.EnumerateFileSystemEntries(Path.GetFullPath(Path.Combine(SystemPath, "../.."))).ToList();
         Assert.Equal(expectedPaths, paths);
     }
-    
+
     [SkippableFact]
     public void TestFileWindowsExceptions()
     {
@@ -552,4 +552,14 @@ public void TestFileSymlink()
             SafeDeleteFile(systemPathDest);
         }
     }
+
+    [Fact]
+    public void TestResolvePath()
+    {
+        var fs = new PhysicalFileSystem();
+        var testPath = fs.ConvertPathFromInternal(SystemPath);
+        var (resFs, resPath) = fs.ResolvePath(testPath);
+        Assert.Equal(testPath, resPath);
+        Assert.Equal(fs, resFs);
+    }
 }

src/Zio.Tests/FileSystems/TestSubFileSystem.cs

@@ -1,5 +1,5 @@
 // Copyright (c) Alexandre Mutel. All rights reserved.
-// This file is licensed under the BSD-Clause 2 license. 
+// This file is licensed under the BSD-Clause 2 license.
 // See the license.txt file in the project root for more information.
 
 using System.IO;
@@ -36,7 +36,7 @@ public void TestBasic()
         }
 
         // TODO: We could add another test just to make sure that files can be created...etc. But the test above should already cover the code provided in SubFileSystem
-    } 
+    }
 
     [Fact]
     public void TestGetOrCreateFileSystem()
@@ -74,6 +74,27 @@ public void TestWatcher()
         Assert.True(gotChange);
     }
 
+    [Fact]
+    public void TestResolvePath()
+    {
+        var fs = GetCommonMemoryFileSystem();
+        var subFs = fs.GetOrCreateSubFileSystem("/a/b");
+        var (resFs, resPath) = subFs.ResolvePath("/c");
+        Assert.Equal("/a/b/c", resPath);
+        Assert.NotEqual(subFs, resFs);
+        Assert.Equal(fs, resFs);
+        (resFs, resPath) = subFs.ResolvePath("/c/d");
+        Assert.Equal("/a/b/c/d", resPath);
+        Assert.NotEqual(subFs, resFs);
+        Assert.Equal(fs, resFs);
+
+        var subFs2 = subFs.GetOrCreateSubFileSystem("/q");
+        (resFs, resPath) = subFs2.ResolvePath("/c");
+        Assert.Equal("/a/b/q/c", resPath);
+        Assert.NotEqual(subFs2, resFs);
+        Assert.Equal(fs, resFs);
+    }
+
     [SkippableFact]
     public void TestDirectorySymlink()
     {

src/Zio.Tests/Zio.Tests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFrameworks>net472;net8.0</TargetFrameworks>
+    <TargetFrameworks>net8.0;net472</TargetFrameworks>
     <IsPackable>false</IsPackable>
     <LangVersion>10</LangVersion>
   </PropertyGroup>