py3: fix int formatting of "incoming changes" log

mercurial/changegroup.py

@@ -411,7 +411,7 b' class cg1unpacker(object):'
                     newheads = [h for h in repo.heads()
                                 if h not in oldheads]
                     repo.ui.log("incoming",
-                                "%s incoming changes - new heads: %s\n",
+                                "%d incoming changes - new heads: %s\n",
                                 len(added),
                                 ', '.join([hex(c[:6]) for c in newheads]))