Refactor for more clarity

src/calibre/utils/copy_files.py

@@ -200,6 +200,40 @@ def copy_files(src_to_dest_map: Dict[str, str], delete_source: bool = False) ->
         copier.copy_all()
 
 
+def register_folder_recursively(
+    src: str, copier: Union[UnixFileCopier, WindowsFileCopier], dest_dir: str,
+    transform_destination_filename: Callable[[str, str], str] = lambda src_path, dest_path : dest_path,
+) -> None:
+
+    def dest_from_entry(dirpath: str, x: str) -> str:
+        path = os.path.join(dirpath, x)
+        rel = os.path.relpath(path, src)
+        return os.path.join(dest_dir, rel)
+
+    def raise_error(e: OSError) -> None:
+        raise e
+
+    copier.register_folder(src)
+    for (dirpath, dirnames, filenames) in os.walk(src, onerror=raise_error):
+        for d in dirnames:
+            path = os.path.join(dirpath, d)
+            dest = dest_from_entry(dirpath, d)
+            os.makedirs(make_long_path_useable(dest), exist_ok=True)
+            shutil.copystat(make_long_path_useable(path), make_long_path_useable(dest), follow_symlinks=False)
+            copier.register_folder(path)
+        for f in filenames:
+            path = os.path.join(dirpath, f)
+            dest = dest_from_entry(dirpath, f)
+            dest = transform_destination_filename(path, dest)
+            if not iswindows:
+                s = os.stat(path, follow_symlinks=False)
+                if stat.S_ISLNK(s.st_mode):
+                    link_dest = os.readlink(path)
+                    os.symlink(link_dest, dest)
+                    continue
+            copier.register(path, dest)
+
+
 def copy_tree(
     src: str, dest: str,
     transform_destination_filename: Callable[[str, str], str] = lambda src_path, dest_path : dest_path,
@@ -222,36 +256,8 @@ def copy_tree(
         raise ValueError(f'Cannot copy tree if the source and destination are the same: {src!r} == {dest!r}')
     dest_dir = dest
 
-    def raise_error(e: OSError) -> None:
-        raise e
-
-    def dest_from_entry(dirpath: str, x: str) -> str:
-        path = os.path.join(dirpath, x)
-        rel = os.path.relpath(path, src)
-        return os.path.join(dest_dir, rel)
-
-
     copier = get_copier(delete_source)
-    copier.register_folder(src)
+    register_folder_recursively(src, copier, dest_dir, transform_destination_filename)
-    for (dirpath, dirnames, filenames) in os.walk(src, onerror=raise_error):
-        for d in dirnames:
-            path = os.path.join(dirpath, d)
-            dest = dest_from_entry(dirpath, d)
-            os.makedirs(make_long_path_useable(dest), exist_ok=True)
-            shutil.copystat(make_long_path_useable(path), make_long_path_useable(dest), follow_symlinks=False)
-            copier.register_folder(path)
-        for f in filenames:
-            path = os.path.join(dirpath, f)
-            dest = dest_from_entry(dirpath, f)
-            dest = transform_destination_filename(path, dest)
-            if not iswindows:
-                s = os.stat(path, follow_symlinks=False)
-                if stat.S_ISLNK(s.st_mode):
-                    link_dest = os.readlink(path)
-                    os.symlink(link_dest, dest)
-                    continue
-            copier.register(path, dest)
-
 
     with copier:
         copier.copy_all()