diff --git a/git/config.py b/git/config.py
@@ -203,7 +203,8 @@ def __setitem__(self, key: str, value: _T) -> None:
    def add(self, key: str, value: Any) -> None:
        if key not in self:
            super().__setitem__(key, [value])
-            return None
        super().__getitem__(key).append(value)

    def setall(self, key: str, values: List[_T]) -> None:
@@ -579,7 +580,7 @@ def read(self) -> None:  # type: ignore[override]
        :raise IOError: If a file cannot be handled
        """
        if self._is_initialized:
-            return None
        self._is_initialized = True

        files_to_read: List[Union[PathLike, IO]] = [""]
@@ -697,7 +698,7 @@ def write(self) -> None:
            a file lock"""
        self._assure_writable("write")
        if not self._dirty:
-            return None

        if isinstance(self._file_or_files, (list, tuple)):
            raise AssertionError(
@@ -711,7 +712,7 @@ def write(self) -> None:
                "Skipping write-back of configuration file as include files were merged in."
                + "Set merge_includes=False to prevent this."
            )
-            return None
        # END stop if we have include files

        fp = self._file_or_files

diff --git a/git/index/base.py b/git/index/base.py
@@ -166,7 +166,7 @@ def _set_cache_(self, attr: str) -> None:
            except OSError:
                # In new repositories, there may be no index, which means we are empty.
                self.entries: Dict[Tuple[PathLike, StageType], IndexEntry] = {}
-                return None
            # END exception handling

            try:
@@ -1210,9 +1210,9 @@ def checkout(
        def handle_stderr(proc: "Popen[bytes]", iter_checked_out_files: Iterable[PathLike]) -> None:
            stderr_IO = proc.stderr
            if not stderr_IO:
-                return None  # Return early if stderr empty.
-            else:
-                stderr_bytes = stderr_IO.read()
            # line contents:
            stderr = stderr_bytes.decode(defenc)
            # git-checkout-index: this already exists

diff --git a/git/index/fun.py b/git/index/fun.py
@@ -83,7 +83,7 @@ def run_commit_hook(name: str, index: "IndexFile", *args: str) -> None:
    """
    hp = hook_path(name, index.repo.git_dir)
    if not os.access(hp, os.X_OK):
-        return None

    env = os.environ.copy()
    env["GIT_INDEX_FILE"] = safe_decode(str(index.path))

diff --git a/git/objects/tree.py b/git/objects/tree.py
@@ -68,7 +68,7 @@ def git_cmp(t1: TreeCacheTup, t2: TreeCacheTup) -> int:

def merge_sort(a: List[TreeCacheTup], cmp: Callable[[TreeCacheTup, TreeCacheTup], int]) -> None:
    if len(a) < 2:
-        return None

    mid = len(a) // 2
    lefthalf = a[:mid]

diff --git a/git/objects/util.py b/git/objects/util.py
@@ -500,8 +500,8 @@ def addToStack(
            depth: int,
        ) -> None:
            lst = self._get_intermediate_items(item)
-            if not lst:  # empty list
-                return None
            if branch_first:
                stack.extendleft(TraverseNT(depth, i, src_item) for i in lst)
            else:

diff --git a/git/util.py b/git/util.py
@@ -644,7 +644,7 @@ def _parse_progress_line(self, line: AnyStr) -> None:
            self.line_dropped(line_str)
            # Note: Don't add this line to the other lines, as we have to silently
            # drop it.
-            return None
        # END handle op code

        # Figure out stage.