Fix missing leading slash due to `relative_to()` resolution

diff --git a/black.py b/black.py
index b3b37ef3295687460e646679c0683c753e89926a..e59a1e5b6f4a291d2c46252ad419c93a6435a019 100644 (file)
--- a/black.py
+++ b/black.py
@@ -2826,7 +2826,7 @@ def gen_python_files_in_dir(
     """
     assert root.is_absolute(), f"INTERNAL ERROR: `root` must be absolute but is {root}"
     for child in path.iterdir():
-        normalized_path = child.resolve().relative_to(root).as_posix()
+        normalized_path = "/" + child.resolve().relative_to(root).as_posix()
         if child.is_dir():
             normalized_path += "/"
         exclude_match = exclude.search(normalized_path)