GH-130614: pathlib ABCs: improve support for receiving path metadata (#131259)

In the private pathlib ABCs, replace `_WritablePath._write_info()` with
`_WritablePath._copy_from()`. This provides the target path object with
more control over the copying process, including support for querying and
setting metadata *before* the path is created.

Adjust `_ReadablePath.copy()` so that it forwards its keyword arguments to
`_WritablePath._copy_from()` of the target path object. This allows us to
remove the unimplemented *preserve_metadata* argument in the ABC method,
making it a `Path` exclusive.

Lib/pathlib/types.py

@@ -12,8 +12,8 @@
 
 from abc import ABC, abstractmethod
 from glob import _PathGlobber
+from pathlib._os import magic_open, ensure_distinct_paths, ensure_different_files, copyfileobj
 from pathlib import PurePath, Path
-from pathlib._os import magic_open, ensure_distinct_paths, copy_file
 from typing import Optional, Protocol, runtime_checkable
 
 
@@ -332,18 +332,21 @@ def readlink(self):
         """
         raise NotImplementedError
 
-    def copy(self, target, follow_symlinks=True, preserve_metadata=False):
+    def copy(self, target, **kwargs):
         """
         Recursively copy this file or directory tree to the given destination.
         """
         if not hasattr(target, 'with_segments'):
             target = self.with_segments(target)
         ensure_distinct_paths(self, target)
-        copy_file(self, target, follow_symlinks, preserve_metadata)
+        try:
+            copy_to_target = target._copy_from
+        except AttributeError:
+            raise TypeError(f"Target path is not writable: {target!r}") from None
+        copy_to_target(self, **kwargs)
         return target.joinpath()  # Empty join to ensure fresh metadata.
 
-    def copy_into(self, target_dir, *, follow_symlinks=True,
-                  preserve_metadata=False):
+    def copy_into(self, target_dir, **kwargs):
         """
         Copy this file or directory tree into the given existing directory.
         """
@@ -354,8 +357,7 @@ def copy_into(self, target_dir, *, follow_symlinks=True,
             target = target_dir / name
         else:
             target = self.with_segments(target_dir, name)
-        return self.copy(target, follow_symlinks=follow_symlinks,
-                         preserve_metadata=preserve_metadata)
+        return self.copy(target, **kwargs)
 
 
 class _WritablePath(_JoinablePath):
@@ -409,11 +411,25 @@ def write_text(self, data, encoding=None, errors=None, newline=None):
         with magic_open(self, mode='w', encoding=encoding, errors=errors, newline=newline) as f:
             return f.write(data)
 
-    def _write_info(self, info, follow_symlinks=True):
+    def _copy_from(self, source, follow_symlinks=True):
         """
-        Write the given PathInfo to this path.
+        Recursively copy the given path to this path.
         """
-        pass
+        stack = [(source, self)]
+        while stack:
+            src, dst = stack.pop()
+            if not follow_symlinks and src.info.is_symlink():
+                dst.symlink_to(str(src.readlink()), src.info.is_dir())
+            elif src.info.is_dir():
+                children = src.iterdir()
+                dst.mkdir()
+                for child in children:
+                    stack.append((child, dst.joinpath(child.name)))
+            else:
+                ensure_different_files(src, dst)
+                with magic_open(src, 'rb') as source_f:
+                    with magic_open(dst, 'wb') as target_f:
+                        copyfileobj(source_f, target_f)
 
 
 _JoinablePath.register(PurePath)