--- a/mercurial/mdiff.py	Fri Mar 06 10:52:44 2020 +0100
+++ b/mercurial/mdiff.py	Fri Mar 06 13:27:41 2020 -0500
@@ -91,7 +91,7 @@
             )
 
     def copy(self, **kwargs):
-        opts = dict((k, getattr(self, k)) for k in self.defaults)
+        opts = {k: getattr(self, k) for k in self.defaults}
         opts = pycompat.strkwargs(opts)
         opts.update(kwargs)
         return diffopts(**opts)