Make pre-commit scripts more OS-agnostic (#6724)

# Description of Changes
Fix #6723

scripts/pre-commit/whitespace.py

@@ -3,11 +3,14 @@
 
 Replaces the end-of-file-fixer / trailing-whitespace pre-commit hooks, which
 have no read-only mode. Run via `task pre-commit` (check) and `task
-pre-commit:fix`; Task selects the files (with `git ls-files`) and passes them
-as arguments.
+pre-commit:fix`.
 
-    python scripts/whitespace.py <files>...          # check: report, exit 1 if any need fixing
-    python scripts/whitespace.py --fix <files>...     # fix: rewrite in place
+Takes git pathspecs (not a file list) and runs `git ls-files` itself, so the
+matched files never hit the command line - on Windows that list can be ~66KB
+and exceed the ~32KB CreateProcess argv limit.
+
+    python whitespace.py <pathspec>...          # check: report, exit 1 if any need fixing
+    python whitespace.py --fix <pathspec>...     # fix: rewrite in place
 
 Operates on bytes and only ever touches trailing spaces/tabs and the final
 newline, so it never mangles content or line endings. Binary files (those with
@@ -16,10 +19,21 @@ a NUL byte) are skipped.
 
 from __future__ import annotations
 
+import subprocess
 import sys
 from pathlib import Path
 
 
+def tracked_files(pathspecs: list[str]) -> list[str]:
+    result = subprocess.run(
+        ["git", "ls-files", "-z", *pathspecs],
+        check=True,
+        capture_output=True,
+        text=True,
+    )
+    return [path for path in result.stdout.split("\0") if path]
+
+
 def normalise(data: bytes) -> bytes:
     # Strip trailing spaces/tabs from each line (leave \r so CRLF survives).
     lines = [line.rstrip(b" \t") for line in data.split(b"\n")]
@@ -32,10 +46,10 @@ def normalise(data: bytes) -> bytes:
 def main() -> int:
     args = sys.argv[1:]
     fix = "--fix" in args
-    paths = [a for a in args if a != "--fix"]
+    pathspecs = [a for a in args if a != "--fix"]
 
     offenders: list[str] = []
-    for path in paths:
+    for path in tracked_files(pathspecs):
         data = Path(path).read_bytes()
         if b"\0" in data:
             continue