Merge branch '5.x'

# Conflicts:
#	sphinx/ext/autodoc/__init__.py
#	sphinx/writers/html5.py

1 files changed, 1 insertions, 1 deletions

diff --git a/sphinx/util/osutil.py b/sphinx/util/osutil.py
index d0ed42c8c..bfc80adcf 100644
--- a/sphinx/util/osutil.py
+++ b/sphinx/util/osutil.py
@@ -112,7 +112,7 @@ def make_filename_from_project(project: str) -> str:
     return make_filename(project_suffix_re.sub('', project)).lower()
 
 
-def relpath(path: str, start: str = os.curdir) -> str:
+def relpath(path: str, start: Optional[str] = os.curdir) -> str:
     """Return a relative filepath to *path* either from the current directory or
     from an optional *start* directory.