Improve how imports and __all__ are written in git.util

+ Update the detailed comment about the unused import situation.

git/util.py

@@ -3,6 +3,32 @@
 # This module is part of GitPython and is released under the
 # 3-Clause BSD License: https://opensource.org/license/bsd-3-clause/
 
+import sys
+
+__all__ = [
+    "stream_copy",
+    "join_path",
+    "to_native_path_linux",
+    "join_path_native",
+    "Stats",
+    "IndexFileSHA1Writer",
+    "IterableObj",
+    "IterableList",
+    "BlockingLockFile",
+    "LockFile",
+    "Actor",
+    "get_user_id",
+    "assure_directory_exists",
+    "RemoteProgress",
+    "CallableRemoteProgress",
+    "rmtree",
+    "unbare_repo",
+    "HIDE_WINDOWS_KNOWN_ERRORS",
+]
+
+if sys.platform == "win32":
+    __all__.append("to_native_path_windows")
+
 from abc import abstractmethod
 import contextlib
 from functools import wraps
@@ -16,11 +42,27 @@
 import shutil
 import stat
 import subprocess
-import sys
 import time
 from urllib.parse import urlsplit, urlunsplit
 import warnings
 
+# NOTE: Unused imports can be improved now that CI testing has fully resumed. Some of
+# these be used indirectly through other GitPython modules, which avoids having to write
+# gitdb all the time in their imports. They are not in __all__, at least currently,
+# because they could be removed or changed at any time, and so should not be considered
+# conceptually public to code outside GitPython. Linters of course do not like it.
+from gitdb.util import (  # noqa: F401  # @IgnorePep8
+    LazyMixin,  # @UnusedImport
+    LockedFD,  # @UnusedImport
+    bin_to_hex,  # @UnusedImport
+    file_contents_ro_filepath,  # @UnusedImport
+    file_contents_ro,  # @UnusedImport
+    hex_to_bin,  # @UnusedImport
+    make_sha,
+    to_bin_sha,  # @UnusedImport
+    to_hex_sha,  # @UnusedImport
+)
+
 # typing ---------------------------------------------------------
 
 from typing import (
@@ -37,73 +79,36 @@
     Pattern,
     Sequence,
     Tuple,
+    TYPE_CHECKING,
     TypeVar,
     Union,
-    TYPE_CHECKING,
     cast,
     overload,
 )
 
 if TYPE_CHECKING:
+    from git.cmd import Git
+    from git.config import GitConfigParser, SectionConstraint
     from git.remote import Remote
     from git.repo.base import Repo
-    from git.config import GitConfigParser, SectionConstraint
-    from git import Git
 
-from .types import (
+from git.types import (
+    Files_TD,
+    Has_id_attribute,
+    HSH_TD,
     Literal,
-    SupportsIndex,
-    Protocol,
-    runtime_checkable,  # because behind py version guards
     PathLike,
-    HSH_TD,
+    Protocol,
+    SupportsIndex,
     Total_TD,
-    Files_TD,  # aliases
-    Has_id_attribute,
+    runtime_checkable,
 )
 
 # ---------------------------------------------------------------------
 
-from gitdb.util import (  # noqa: F401  # @IgnorePep8
-    make_sha,
-    LockedFD,  # @UnusedImport
-    file_contents_ro,  # @UnusedImport
-    file_contents_ro_filepath,  # @UnusedImport
-    LazyMixin,  # @UnusedImport
-    to_hex_sha,  # @UnusedImport
-    to_bin_sha,  # @UnusedImport
-    bin_to_hex,  # @UnusedImport
-    hex_to_bin,  # @UnusedImport
-)
-
 T_IterableObj = TypeVar("T_IterableObj", bound=Union["IterableObj", "Has_id_attribute"], covariant=True)
 # So IterableList[Head] is subtype of IterableList[IterableObj].
 
-# NOTE:  Some of the unused imports might be used/imported by others.
-# Handle once test-cases are back up and running.
-# Most of these are unused here, but are for use by git-python modules so these
-# don't see gitdb all the time. Flake of course doesn't like it.
-__all__ = [
-    "stream_copy",
-    "join_path",
-    "to_native_path_linux",
-    "join_path_native",
-    "Stats",
-    "IndexFileSHA1Writer",
-    "IterableObj",
-    "IterableList",
-    "BlockingLockFile",
-    "LockFile",
-    "Actor",
-    "get_user_id",
-    "assure_directory_exists",
-    "RemoteProgress",
-    "CallableRemoteProgress",
-    "rmtree",
-    "unbare_repo",
-    "HIDE_WINDOWS_KNOWN_ERRORS",
-]
-
 _logger = logging.getLogger(__name__)
 
 
@@ -292,7 +297,6 @@ def to_native_path_linux(path: PathLike) -> str:
         path = str(path)
         return path.replace("\\", "/")
 
-    __all__.append("to_native_path_windows")
     to_native_path = to_native_path_windows
 else:
     # No need for any work on Linux.