fix: accept current-directory files in parent assurance

`assure_directory_exists("notes.txt", is_file=True)` attempted to create the empty dirname and raised `FileNotFoundError`, despite the current directory already being present.

Interpret an empty parent as `os.curdir` for file inputs. Preserve the helper's return convention, nested parent creation and failures when a parent is an existing regular file.

Use a native scripted filesystem fixture for string and pathlib inputs. Two current-directory cases fail before the fix, while six controls pass. All eight cases pass afterward; utility and typing modules pass on both backends (129 passed, 39 skipped each). Applicable pre-commit checks, including shellcheck, pass.

Assisted-by: OpenAI Codex (model: unknown, autonomous)

Author: gavenren

git/util.py

@@ -402,7 +402,7 @@ def assure_directory_exists(path: PathLike, is_file: bool = False) -> bool:
         ``True`` if the directory was created, ``False`` if it already existed.
     """
     if is_file:
-        path = osp.dirname(path)
+        path = osp.dirname(path) or osp.curdir
     # END handle file
     if not osp.isdir(path):
         os.makedirs(path, exist_ok=True)

test/test_assure_directory.py

@@ -0,0 +1,42 @@
+from pathlib import Path
+
+import pytest
+
+from git.util import assure_directory_exists
+from test.lib.fixtures import writable_fixture
+
+
+@pytest.fixture
+def directory_fixture(monkeypatch):
+    with writable_fixture("assure-directory.sh") as temporary:
+        directory = temporary.path().resolve()
+        with monkeypatch.context() as context:
+            context.chdir(directory)
+            yield directory
+
+
+@pytest.mark.parametrize("path_type", [str, Path])
+def test_file_in_current_directory_already_has_parent(directory_fixture, path_type):
+    assert assure_directory_exists(path_type("notes.txt"), is_file=True) is False
+    assert not (directory_fixture / "notes.txt").exists()
+
+
+@pytest.mark.parametrize("path_type", [str, Path])
+def test_nested_file_creates_only_missing_parent_directories(directory_fixture, path_type):
+    filename = path_type("new/nested/notes.txt")
+    assert assure_directory_exists(filename, is_file=True) is True
+    assert (directory_fixture / "new/nested").is_dir()
+    assert not (directory_fixture / "new/nested/notes.txt").exists()
+    assert assure_directory_exists(filename, is_file=True) is False
+
+
+@pytest.mark.parametrize("path_type", [str, Path])
+def test_existing_directory_is_unchanged(directory_fixture, path_type):
+    assert assure_directory_exists(path_type("existing")) is False
+
+
+@pytest.mark.parametrize("path_type", [str, Path])
+def test_file_cannot_be_used_as_parent_directory(directory_fixture, path_type):
+    with pytest.raises(FileExistsError):
+        assure_directory_exists(path_type("blocked/notes.txt"), is_file=True)
+    assert (directory_fixture / "blocked").read_text() == "occupied\n"

tests/fixtures/assure-directory.sh

@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+set -eu
+mkdir existing
+printf 'occupied\n' > blocked