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}"

betterproto/tests/test_get_ref_type.py

@@ -242,6 +242,26 @@ def test_import_cousin_package():
     assert name == "_y.Message"
 
 
+def test_import_cousin_package_different_name():
+    imports = set()
+    name = get_ref_type(
+        package="test.package1", imports=imports, source_type="cousin.package2.Message"
+    )
+
+    assert imports == {"from ...cousin import package2 as __cousin_package2"}
+    assert name == "__cousin_package2.Message"
+
+
+def test_import_cousin_package_same_name():
+    imports = set()
+    name = get_ref_type(
+        package="test.package", imports=imports, source_type="cousin.package.Message"
+    )
+
+    assert imports == {"from ...cousin import package as __cousin_package"}
+    assert name == "__cousin_package.Message"
+
+
 def test_import_far_cousin_package():
     imports = set()
     name = get_ref_type(package="a.x.y", imports=imports, source_type="a.b.c.Message")