[fs] Add RenameDirectory support for same-parent directory renaming (#4312)

- [x] I have read and followed the [Contribution Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/CONTRIBUTING.md#code-contributions).
- [x] I have read and followed the [AI Policy](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/AI.md)
- [x] I have read and followed the [Coding Guidelines](https://git.eden-emu.dev/eden-emu/eden/src/branch/master/docs/policies/Coding.md) to the best of my ability.

-------------------
Fixes save corruption in Warhammer 40k: Mechanicus and other games
that rename directories within the same parent folder.

- Added RenameDirectory handler in IFileSystem (command 6)
- Implemented same-parent directory renaming using RenameDir

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/4312
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Reviewed-by: Samuel <lizzie@eden-emu.dev>

3 files changed, 20 insertions, 6 deletions

diff --git a/src/core/hle/service/filesystem/filesystem.cpp b/src/core/hle/service/filesystem/filesystem.cpp
index d5984f560b..20e050c8a8 100644
--- a/src/core/hle/service/filesystem/filesystem.cpp
+++ b/src/core/hle/service/filesystem/filesystem.cpp
@@ -227,12 +227,13 @@ Result VfsDirectoryServiceWrapper::RenameDirectory(const std::string& src_path_,
     std::string src_path(Common::FS::SanitizePath(src_path_));
     std::string dest_path(Common::FS::SanitizePath(dest_path_));
     auto src = GetDirectoryRelativeWrapped(backing, src_path);
+    if (src == nullptr)
+        return FileSys::ResultPathNotFound;
+
     if (Common::FS::GetParentPath(src_path) == Common::FS::GetParentPath(dest_path)) {
-        // Use more-optimized vfs implementation rename.
-        if (src == nullptr)
-            return FileSys::ResultPathNotFound;
-        if (!src->Rename(Common::FS::GetFilename(dest_path))) {
-            // TODO(DarkLordZach): Find a better error code for this
+        std::string full_src_path = backing->GetFullPath() + "/" + src_path;
+        std::string full_dest_path = backing->GetFullPath() + "/" + dest_path;
+        if (!Common::FS::RenameDir(full_src_path, full_dest_path)) {
             return ResultUnknown;
         }
         return ResultSuccess;
diff --git a/src/core/hle/service/filesystem/fsp/fs_i_filesystem.cpp b/src/core/hle/service/filesystem/fsp/fs_i_filesystem.cpp
index d16602022a..edd381f57c 100644
--- a/src/core/hle/service/filesystem/fsp/fs_i_filesystem.cpp
+++ b/src/core/hle/service/filesystem/fsp/fs_i_filesystem.cpp
@@ -24,7 +24,7 @@ IFileSystem::IFileSystem(Core::System& system_, FileSys::VirtualDir dir_, SizeGe
         {3, D<&IFileSystem::DeleteDirectory>, "DeleteDirectory"},
         {4, D<&IFileSystem::DeleteDirectoryRecursively>, "DeleteDirectoryRecursively"},
         {5, D<&IFileSystem::RenameFile>, "RenameFile"},
-        {6, nullptr, "RenameDirectory"},
+        {6, D<&IFileSystem::RenameDirectory>, "RenameDirectory"},
         {7, D<&IFileSystem::GetEntryType>, "GetEntryType"},
         {8, D<&IFileSystem::OpenFile>, "OpenFile"},
         {9, D<&IFileSystem::OpenDirectory>, "OpenDirectory"},
@@ -88,6 +88,14 @@ Result IFileSystem::RenameFile(
     R_RETURN(backend->RenameFile(FileSys::Path(old_path->str), FileSys::Path(new_path->str)));
 }
 
+Result IFileSystem::RenameDirectory(
+    const InLargeData<FileSys::Sf::Path, BufferAttr_HipcPointer> old_path,
+    const InLargeData<FileSys::Sf::Path, BufferAttr_HipcPointer> new_path) {
+    LOG_DEBUG(Service_FS, "called. directory '{}' to directory '{}'", old_path->str, new_path->str);
+
+    R_RETURN(backend->RenameDirectory(FileSys::Path(old_path->str), FileSys::Path(new_path->str)));
+}
+
 Result IFileSystem::OpenFile(OutInterface<IFile> out_interface,
                              const InLargeData<FileSys::Sf::Path, BufferAttr_HipcPointer> path,
                              u32 mode) {
diff --git a/src/core/hle/service/filesystem/fsp/fs_i_filesystem.h b/src/core/hle/service/filesystem/fsp/fs_i_filesystem.h
index dd069f36f3..ed03c3ef83 100644
--- a/src/core/hle/service/filesystem/fsp/fs_i_filesystem.h
+++ b/src/core/hle/service/filesystem/fsp/fs_i_filesystem.h
@@ -1,3 +1,6 @@
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
+// SPDX-License-Identifier: GPL-3.0-or-later
+
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
 // SPDX-License-Identifier: GPL-2.0-or-later
 
@@ -36,6 +39,8 @@ public:
         const InLargeData<FileSys::Sf::Path, BufferAttr_HipcPointer> path);
     Result RenameFile(const InLargeData<FileSys::Sf::Path, BufferAttr_HipcPointer> old_path,
                       const InLargeData<FileSys::Sf::Path, BufferAttr_HipcPointer> new_path);
+    Result RenameDirectory(const InLargeData<FileSys::Sf::Path, BufferAttr_HipcPointer> old_path,
+                           const InLargeData<FileSys::Sf::Path, BufferAttr_HipcPointer> new_path);
     Result OpenFile(OutInterface<IFile> out_interface,
                     const InLargeData<FileSys::Sf::Path, BufferAttr_HipcPointer> path, u32 mode);
     Result OpenDirectory(OutInterface<IDirectory> out_interface,