chore: import upstream snapshot with attribution

tests/test_long_path_hashing.py

@@ -0,0 +1,50 @@
+r"""#1655 — files whose absolute path exceeds Windows MAX_PATH (260) must still
+be hashed, or their manifest entry never stabilizes and detect_incremental
+re-flags them as changed on every run.
+
+The plain file APIs reject long paths on win32 unless prefixed with the
+extended-length marker `\\?\`. _os_path adds it (for I/O), the mirror of
+cache._normalize_path which strips it (for stable keys).
+"""
+from __future__ import annotations
+
+from pathlib import Path
+
+from graphify import detect
+
+
+def test_os_path_noop_on_posix(monkeypatch):
+    monkeypatch.setattr("sys.platform", "linux")
+    p = Path("/home/user/deep/file.py")
+    assert detect._os_path(p) == str(p)
+
+
+def test_os_path_adds_prefix_on_win32(monkeypatch):
+    monkeypatch.setattr("sys.platform", "win32")
+    # os.path.abspath is posix here, so exercise the already-qualified branch:
+    # a value that abspath leaves intact still gets the prefix.
+    out = detect._os_path(Path("/already/abs/file.py"))
+    assert out.startswith("\\\\?\\")
+
+
+def test_os_path_idempotent_on_win32(monkeypatch):
+    monkeypatch.setattr("sys.platform", "win32")
+    already = "\\\\?\\C:\\a\\file.py"
+    assert detect._os_path(Path(already)) == already
+
+
+def test_hashing_still_works_and_stabilizes(tmp_path):
+    # End-to-end (posix): a hashed file must produce a stable, non-empty hash so
+    # its manifest entry doesn't churn. Guards against the _os_path indirection
+    # breaking normal hashing.
+    f = tmp_path / "deep" / "nested" / "module.py"
+    f.parent.mkdir(parents=True)
+    f.write_text("def x():\n    return 1\n")
+    h1 = detect._md5_file(f)
+    h2 = detect._md5_file(f)
+    assert h1 and h1 == h2
+
+    got = detect._stat_and_hash(str(f))
+    assert got is not None
+    assert got[0] == str(f)
+    assert got[2] == h1