Fix other submodule.base parent_commit annotations

This finishes the work in git.objects.submodule.base begun in
1541c62. Some remaining occurrences of the old Commit_ish type are
in git.objects.submodule.root, which still need to be replaced.

Even once that is done, this will not have fixed #1869, though it
will be somewhat mitigated because each method's annotations
related to parent_commit will reflect the types that can actually
be used reliably under the current implementation, even if in some
cases that may not be as broad as was meant, or hoped, to be
supported. I expect this may lead the way to a fix for #1869, since
the existing behavior and relationships will be clearer.

Where the old Commit_ish annotations were changed here to "Commit",
it reflects assumptions found by examining the implementation that
other alternatives are not usable becuse something beloning to a
Commit is used and no conversion or fallback is performed for it.
Where a commit is looked up (which uses rev_parse), broader types
are annotated. Where the argument is used without conversion and
must have a `tree` attribute, it must be a Commit. Where the
argument could be broader but must be compared meaningfully with
something known to be a commit, it must at minimum have a binsha
attribute to allow that equality comparison, implemented in Object,
to be meaningful, so in such cases its type cannot include str.

Author: EliahKagan

git/objects/submodule/base.py

@@ -42,10 +42,19 @@
 
 # typing ----------------------------------------------------------------------
 
-from typing import Callable, Dict, Mapping, Sequence, TYPE_CHECKING, cast
-from typing import Any, Iterator, Union
+from typing import (
+    Any,
+    Callable,
+    Dict,
+    Iterator,
+    Mapping,
+    Sequence,
+    TYPE_CHECKING,
+    Union,
+    cast,
+)
 
-from git.types import Commit_ish, Literal, Old_commit_ish, PathLike, TBD
+from git.types import Commit_ish, Literal, PathLike, TBD
 
 if TYPE_CHECKING:
     from git.index import IndexFile
@@ -113,7 +122,7 @@ def __init__(
         mode: Union[int, None] = None,
         path: Union[PathLike, None] = None,
         name: Union[str, None] = None,
-        parent_commit: Union[Old_commit_ish, None] = None,
+        parent_commit: Union["Commit", None] = None,
         url: Union[str, None] = None,
         branch_path: Union[PathLike, None] = None,
     ) -> None:
@@ -145,7 +154,6 @@ def __init__(
         if url is not None:
             self._url = url
         if branch_path is not None:
-            # assert isinstance(branch_path, str)
             self._branch_path = branch_path
         if name is not None:
             self._name = name
@@ -214,7 +222,7 @@ def __repr__(self) -> str:
 
     @classmethod
     def _config_parser(
-        cls, repo: "Repo", parent_commit: Union[Old_commit_ish, None], read_only: bool
+        cls, repo: "Repo", parent_commit: Union["Commit", None], read_only: bool
     ) -> SubmoduleConfigParser:
         """
         :return:
@@ -265,7 +273,7 @@ def _clear_cache(self) -> None:
         # END for each name to delete
 
     @classmethod
-    def _sio_modules(cls, parent_commit: Old_commit_ish) -> BytesIO:
+    def _sio_modules(cls, parent_commit: "Commit") -> BytesIO:
         """
         :return:
             Configuration file as :class:`~io.BytesIO` - we only access it through the
@@ -278,7 +286,7 @@ def _sio_modules(cls, parent_commit: Old_commit_ish) -> BytesIO:
     def _config_parser_constrained(self, read_only: bool) -> SectionConstraint:
         """:return: Config parser constrained to our submodule in read or write mode"""
         try:
-            pc: Union["Old_commit_ish", None] = self.parent_commit
+            pc = self.parent_commit
         except ValueError:
             pc = None
         # END handle empty parent repository