Add new byte-order-marker checker/fixer

pre_commit_hooks/fix_byte_order_marker.py

@@ -0,0 +1,30 @@
+import argparse
+from typing import Optional
+from typing import Sequence
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*', help='Filenames to check')
+    args = parser.parse_args(argv)
+
+    retv = 0
+
+    for filename in args.filenames:
+        with open(filename, 'rb') as f_b:
+            bts = f_b.read(3)
+
+        if bts == b'\xef\xbb\xbf':
+            with open(filename, newline='', encoding='utf-8-sig') as f:
+                contents = f.read()
+            with open(filename, 'w', newline='', encoding='utf-8') as f:
+                f.write(contents)
+
+            print(f'{filename}: removed byte-order marker')
+            retv = 1
+
+    return retv
+
+
+if __name__ == '__main__':
+    exit(main())