Add check_path hook

Adds a hook which can be used for preventing commits to paths specified
by regex.

pre_commit_hooks/check_path_edits.py

@@ -0,0 +1,40 @@
+import argparse
+import re
+from typing import AbstractSet
+from typing import Optional
+from typing import Sequence
+
+from pre_commit_hooks.util import added_files
+
+
+def find_wrong_paths(paths: Sequence[str], patterns: AbstractSet[str]) \
+        -> int:
+    for filename in (added_files() & set(paths)):
+        if patterns:
+            for pattern in patterns:
+                if re.search(pattern, filename):
+                    print(f'Path {filename} prevented by pattern: {pattern}')
+                    return 1
+    return 0
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        'filenames', nargs='*',
+        help='Filenames pre-commit believes are changed.',
+    )
+    parser.add_argument(
+        '-p', '--pattern', action='append',
+        help=(
+            'regex pattern for path to disallow commits to, '
+            'may be specified multiple times'
+        ),
+    )
+
+    args = parser.parse_args(argv)
+    return find_wrong_paths(args.filenames, args.pattern)
+
+
+if __name__ == '__main__':
+    exit(main())