Add __all__ in git.exc, adjust __init__.py imports

The git.exc module imports exceptions from gitdb.exc to republish
them, as well as defining its own (also for use from outside). But
because it did not define __all__, the intent for the exceptions it
imported was unclear, since names that are introduced by imports
and not present in __all__ are not generally considered public,
even when __all__ is absent and a "*" import would reimport them.

This rectifies that by adding __all__ and listing both imported and
newly introduced exceptions explicitly in it. Although this
strictly expands which names are public under typical conventions,
it strictly contracts which names are imported by a "*" import,
because the presence of __all__ suppresses names not listed in it
from being imported that way. However, because under typical
conventions those other names are not considered public, and they
were not even weakly documented as public, this should be okay.

(Even though this is not a breaking change, in that code it would
break would already technically be broken... if it turns out that
it is common to wrongly rely on the availabiliy of those names,
then this may need to be revisited and slightly modified.)

This brings the readily identified public interface of git.exc in
line with what is weakly implied (and intended) by its docstring.

This also modifies __init__.py accordingly: The top-level git
module has for some time used a "*" import on git.exc, causing
the extra names originally meant as implementation details to be
included. Because its own __all__ was dynamically generated until
c862845, #1659 also added 8edc53b to retain the formerly present
names in __all__. So the change here imports those names from the
modules that deliberately provide them, to preserve compatibility.

git/__init__.py

@@ -7,10 +7,10 @@
 # @PydevCodeAnalysisIgnore
 from git.exc import *  # @NoMove @IgnorePep8
 import os
-import sys
 import os.path as osp
+import sys
 
-from typing import Optional
+from typing import List, Optional, Sequence, Tuple, Union, TYPE_CHECKING
 from git.types import PathLike
 
 __version__ = "git"
@@ -38,7 +38,10 @@ def _init_externals() -> None:
 
 # { Imports
 
+from gitdb.util import to_hex_sha
+
 try:
+    from git.compat import safe_decode  # @NoMove @IgnorePep8
     from git.config import GitConfigParser  # @NoMove @IgnorePep8
     from git.objects import *  # @NoMove @IgnorePep8
     from git.refs import *  # @NoMove @IgnorePep8
@@ -53,6 +56,7 @@ def _init_externals() -> None:
         BlockingLockFile,
         Stats,
         Actor,
+        remove_password_if_present,
         rmtree,
     )
 except GitError as _exc:

git/exc.py

@@ -5,7 +5,34 @@
 # the BSD License: https://opensource.org/license/bsd-3-clause/
 """ Module containing all exceptions thrown throughout the git package """
 
-from gitdb.exc import (  # noqa: @UnusedImport
+__all__ = [
+    # Defined in gitdb.exc:
+    "AmbiguousObjectName",
+    "BadName",
+    "BadObject",
+    "BadObjectType",
+    "InvalidDBRoot",
+    "ODBError",
+    "ParseError",
+    "UnsupportedOperation",
+    # Introduced in this module:
+    "GitError",
+    "InvalidGitRepositoryError",
+    "WorkTreeRepositoryUnsupported",
+    "NoSuchPathError",
+    "UnsafeProtocolError",
+    "UnsafeOptionError",
+    "CommandError",
+    "GitCommandNotFound",
+    "GitCommandError",
+    "CheckoutError",
+    "CacheError",
+    "UnmergedEntriesError",
+    "HookExecutionError",
+    "RepositoryDirtyError",
+]
+
+from gitdb.exc import (
     AmbiguousObjectName,
     BadName,
     BadObject,
@@ -14,7 +41,6 @@
     ODBError,
     ParseError,
     UnsupportedOperation,
-    to_hex_sha,
 )
 from git.compat import safe_decode
 from git.util import remove_password_if_present