Re-organize directory structure (#4971)

See discussion in #2491

Co-authored-by: Ivan Levkivskyi <ilevkivskyi@dropbox.com>

stdlib/posixpath.pyi

@@ -0,0 +1,113 @@
+import os
+import sys
+from _typeshed import AnyPath, BytesPath, StrPath
+from builtins import _PathLike
+from genericpath import exists as exists
+from typing import Any, AnyStr, Optional, Sequence, Tuple, TypeVar, overload
+
+_T = TypeVar("_T")
+
+# ----- os.path variables -----
+supports_unicode_filenames: bool
+# aliases (also in os)
+curdir: str
+pardir: str
+sep: str
+if sys.platform == "win32":
+    altsep: str
+else:
+    altsep: Optional[str]
+extsep: str
+pathsep: str
+defpath: str
+devnull: str
+
+# ----- os.path function stubs -----
+# Overloads are necessary to work around python/mypy#3644.
+@overload
+def abspath(path: _PathLike[AnyStr]) -> AnyStr: ...
+@overload
+def abspath(path: AnyStr) -> AnyStr: ...
+@overload
+def basename(p: _PathLike[AnyStr]) -> AnyStr: ...
+@overload
+def basename(p: AnyStr) -> AnyStr: ...
+@overload
+def dirname(p: _PathLike[AnyStr]) -> AnyStr: ...
+@overload
+def dirname(p: AnyStr) -> AnyStr: ...
+@overload
+def expanduser(path: _PathLike[AnyStr]) -> AnyStr: ...
+@overload
+def expanduser(path: AnyStr) -> AnyStr: ...
+@overload
+def expandvars(path: _PathLike[AnyStr]) -> AnyStr: ...
+@overload
+def expandvars(path: AnyStr) -> AnyStr: ...
+@overload
+def normcase(s: _PathLike[AnyStr]) -> AnyStr: ...
+@overload
+def normcase(s: AnyStr) -> AnyStr: ...
+@overload
+def normpath(path: _PathLike[AnyStr]) -> AnyStr: ...
+@overload
+def normpath(path: AnyStr) -> AnyStr: ...
+
+if sys.platform == "win32":
+    @overload
+    def realpath(path: _PathLike[AnyStr]) -> AnyStr: ...
+    @overload
+    def realpath(path: AnyStr) -> AnyStr: ...
+
+else:
+    @overload
+    def realpath(filename: _PathLike[AnyStr]) -> AnyStr: ...
+    @overload
+    def realpath(filename: AnyStr) -> AnyStr: ...
+
+# In reality it returns str for sequences of StrPath and bytes for sequences
+# of BytesPath, but mypy does not accept such a signature.
+def commonpath(paths: Sequence[AnyPath]) -> Any: ...
+
+# NOTE: Empty lists results in '' (str) regardless of contained type.
+# So, fall back to Any
+def commonprefix(m: Sequence[AnyPath]) -> Any: ...
+def lexists(path: AnyPath) -> bool: ...
+
+# These return float if os.stat_float_times() == True,
+# but int is a subclass of float.
+def getatime(filename: AnyPath) -> float: ...
+def getmtime(filename: AnyPath) -> float: ...
+def getctime(filename: AnyPath) -> float: ...
+def getsize(filename: AnyPath) -> int: ...
+def isabs(s: AnyPath) -> bool: ...
+def isfile(path: AnyPath) -> bool: ...
+def isdir(s: AnyPath) -> bool: ...
+def islink(path: AnyPath) -> bool: ...
+def ismount(path: AnyPath) -> bool: ...
+@overload
+def join(a: StrPath, *paths: StrPath) -> str: ...
+@overload
+def join(a: BytesPath, *paths: BytesPath) -> bytes: ...
+@overload
+def relpath(path: BytesPath, start: Optional[BytesPath] = ...) -> bytes: ...
+@overload
+def relpath(path: StrPath, start: Optional[StrPath] = ...) -> str: ...
+def samefile(f1: AnyPath, f2: AnyPath) -> bool: ...
+def sameopenfile(fp1: int, fp2: int) -> bool: ...
+def samestat(s1: os.stat_result, s2: os.stat_result) -> bool: ...
+@overload
+def split(p: _PathLike[AnyStr]) -> Tuple[AnyStr, AnyStr]: ...
+@overload
+def split(p: AnyStr) -> Tuple[AnyStr, AnyStr]: ...
+@overload
+def splitdrive(p: _PathLike[AnyStr]) -> Tuple[AnyStr, AnyStr]: ...
+@overload
+def splitdrive(p: AnyStr) -> Tuple[AnyStr, AnyStr]: ...
+@overload
+def splitext(p: _PathLike[AnyStr]) -> Tuple[AnyStr, AnyStr]: ...
+@overload
+def splitext(p: AnyStr) -> Tuple[AnyStr, AnyStr]: ...
+
+if sys.version_info < (3, 7) and sys.platform == "win32":
+    def splitunc(p: AnyStr) -> Tuple[AnyStr, AnyStr]: ...  # deprecated