validate_patch.py

import re
import sys
from pathlib import Path

p = Path(sys.argv[1]) if len(sys.argv) > 1 else None
if not p or not p.exists():
    print("Usage: python validate_patch.py <patchfile>")
    sys.exit(2)

text = p.read_text(encoding="utf-8", errors="replace")

# Reject markdown fences
if "```" in text:
    print("FAIL: patch contains markdown fences ```")
    sys.exit(1)

# Must have git headers
if "diff --git " not in text:
    print("FAIL: patch missing 'diff --git' header")
    sys.exit(1)

# Must not contain absolute home paths
if "/home/" in text:
    print("FAIL: patch contains absolute paths (/home/...)")
    sys.exit(1)

# Detect naked (unprefixed) lines inside hunks
in_hunk = False
for i, line in enumerate(text.splitlines(True), start=1):
    if line.startswith("@@ "):
        in_hunk = True
        continue
    if in_hunk:
        if line.startswith(("diff --git ", "index ", "--- ", "+++ ")):
            in_hunk = False
            continue
        if not line.startswith(("+", "-", " ", "\\")):
            # This catches your exact issue (blank/whitespace lines with no prefix)
            preview = line.replace("\n", "\\n")
            print(f"FAIL: unprefixed line inside hunk at {i}: {preview!r}")
            sys.exit(1)

print("OK")