DiscIO: Fix recursive directory extraction

https://bugs.dolphin-emu.org/issues/12331

Source/Core/DiscIO/DiscExtractor.cpp

@@ -130,8 +130,10 @@ void ExportDirectory(const Volume& volume, const Partition& partition, const Fil
                      const std::string& export_folder,
                      const std::function<bool(const std::string& path)>& update_progress)
 {
-  const std::string export_root =
-      export_folder + (directory.IsDirectory() ? "/" + directory.GetName() + "/" : "/");
+  std::string export_root = export_folder + '/';
+  if (directory.IsDirectory() && !directory.IsRoot())
+    export_root += directory.GetName() + '/';
+
   File::CreateFullPath(export_root);
 
   for (const FileInfo& file_info : directory)
@@ -154,7 +156,8 @@ void ExportDirectory(const Volume& volume, const Partition& partition, const Fil
     }
     else if (recursive)
     {
-      ExportDirectory(volume, partition, file_info, recursive, path, export_path, update_progress);
+      ExportDirectory(volume, partition, file_info, recursive, filesystem_path, export_root,
+                      update_progress);
     }
   }
 }

Source/Core/DiscIO/FileSystemGCWii.cpp

@@ -96,6 +96,11 @@ u64 FileInfoGCWii::GetOffset() const
   return static_cast<u64>(Get(EntryProperty::FILE_OFFSET)) << m_offset_shift;
 }
 
+bool FileInfoGCWii::IsRoot() const
+{
+  return m_index == 0;
+}
+
 bool FileInfoGCWii::IsDirectory() const
 {
   return (Get(EntryProperty::NAME_OFFSET) & 0xFF000000) != 0;

Source/Core/DiscIO/FileSystemGCWii.h

@@ -42,6 +42,7 @@ public:
 
   u64 GetOffset() const override;
   u32 GetSize() const override;
+  bool IsRoot() const override;
   bool IsDirectory() const override;
   u32 GetTotalChildren() const override;
   std::string GetName() const override;

Source/Core/DiscIO/Filesystem.h

@@ -89,6 +89,7 @@ public:
   virtual u32 GetSize() const = 0;
   // For a file, returns its size. For a directory, returns the total size of its contents.
   u64 GetTotalSize() const;
+  virtual bool IsRoot() const = 0;
   virtual bool IsDirectory() const = 0;
   // The number of files and directories in a directory, including those in subdirectories.
   // Not guaranteed to return a meaningful value for files.