mercurial/cmdutil.py

--- a/mercurial/cmdutil.py	Fri Apr 30 20:21:56 2021 +0200
+++ b/mercurial/cmdutil.py	Fri May 07 08:38:17 2021 -0700
@@ -1851,7 +1851,10 @@
             continue
         copylist.append((tfn(pat, dest, srcs), srcs))
     if not copylist:
-        raise error.InputError(_(b'no files to copy'))
+        hint = None
+        if rename:
+            hint = _(b'maybe you meant to use --after --at-rev=.')
+        raise error.InputError(_(b'no files to copy'), hint=hint)
 
     errors = 0
     for targetpath, srcs in copylist: