Support for sapling scm (#122072)

We can use Sapling (hg) with the pytorch repo but there are a couple minor issues to teach our scripting to be happier with having either a git or hg repo.

This change fixes some issues in:
- setup.py
- lintrunner

Pull Request resolved: https://github.com/pytorch/pytorch/pull/122072
Approved by: https://github.com/ezyang

tools/linter/adapters/clangtidy_linter.py

@@ -13,13 +13,22 @@ from pathlib import Path
 from sysconfig import get_paths as gp
 from typing import Any, List, NamedTuple, Optional, Pattern
 
+
 # PyTorch directory root
-result = subprocess.run(
-    ["git", "rev-parse", "--show-toplevel"],
-    stdout=subprocess.PIPE,
-    check=True,
-)
-PYTORCH_ROOT = result.stdout.decode("utf-8").strip()
+def scm_root() -> str:
+    path = os.path.abspath(os.getcwd())
+    while True:
+        if os.path.isdir(os.path.join(path, ".git")):
+            return path
+        if os.path.isdir(os.path.join(path, ".hg")):
+            return path
+        n = len(path)
+        path = os.path.dirname(path)
+        if len(path) == n:
+            raise RuntimeError("Unable to find SCM root")
+
+
+PYTORCH_ROOT = scm_root()
 IS_WINDOWS: bool = os.name == "nt"