--- a/mercurial/patch.py	Fri Mar 06 10:52:44 2020 +0100
+++ b/mercurial/patch.py	Fri Mar 06 13:27:41 2020 -0500
@@ -2888,7 +2888,7 @@
     or 'rename' (the latter two only if opts.git is set).'''
     gone = set()
 
-    copyto = dict([(v, k) for k, v in copy.items()])
+    copyto = {v: k for k, v in copy.items()}
 
     addedset, removedset = set(added), set(removed)