diff --git a/git/index/base.py b/git/index/base.py
@@ -381,23 +381,21 @@ def from_tree(cls, repo: "Repo", *treeish: Treeish, **kwargs: Any) -> "IndexFile
            arg_list.append("--aggressive")
        # END merge handling

-        # tmp file created in git home directory to be sure renaming
-        # works - /tmp/ dirs could be on another device.
-        with contextlib.ExitStack() as stack:
-            tmp_index = stack.enter_context(_named_temporary_file_for_subprocess(repo.git_dir))
            arg_list.append("--index-output=%s" % tmp_index)
            arg_list.extend(treeish)

-            # Move current index out of the way - otherwise the merge may fail
            # as it considers existing entries. Moving it essentially clears the index.
            # Unfortunately there is no 'soft' way to do it.
            # The TemporaryFileSwap ensures the original file gets put back.
-
-            stack.enter_context(TemporaryFileSwap(join_path_native(repo.git_dir, "index")))
-            repo.git.read_tree(*arg_list, **kwargs)
-            index = cls(repo, tmp_index)
-            index.entries  # Force it to read the file as we will delete the temp-file.
-            return index
            # END index merge handling

    # UTILITIES

diff --git a/git/index/util.py b/git/index/util.py
@@ -15,7 +15,7 @@

from typing import Any, Callable, TYPE_CHECKING, Optional, Type

-from git.types import PathLike, _T

if TYPE_CHECKING:
    from git.index import IndexFile
@@ -55,7 +55,7 @@ def __exit__(
        exc_type: Optional[Type[BaseException]],
        exc_val: Optional[BaseException],
        exc_tb: Optional[TracebackType],
-    ) -> bool:
        if osp.isfile(self.tmp_file_path):
            os.replace(self.tmp_file_path, self.file_path)
        return False