Fixes issue where importing cousin where path has a package with the same name broke import

betterproto/compile/importing.py

@@ -1,3 +1,4 @@
+import os
 import re
 from typing import Dict, List, Type
 
@@ -138,16 +139,14 @@ def import_cousin(current_package, imports, py_package, py_type):
     package = foo.bar.baz
     name    = foo.example.Bar
     """
-    shared_ancestory = [
-        pair[0] for pair in zip(current_package, py_package) if pair[0] == pair[1]
-    ]
-    distance_up = len(current_package) - len(shared_ancestory)
+    shared_ancestry = os.path.commonprefix([current_package, py_package])
+    distance_up = len(current_package) - len(shared_ancestry)
     string_from = f".{'.' * distance_up}" + ".".join(
-        py_package[len(shared_ancestory) : -1]
+        py_package[len(shared_ancestry) : -1]
     )
     string_import = py_package[-1]
     alias = f"{'_' * distance_up}" + safe_snake_case(
-        ".".join(py_package[len(shared_ancestory) :])
+        ".".join(py_package[len(shared_ancestry) :])
     )
     imports.add(f"from {string_from} import {string_import} as {alias}")
     return f"{alias}.{py_type}"