--- a/mercurial/merge.py	Tue Sep 26 13:58:58 2006 +0200
+++ b/mercurial/merge.py	Tue Sep 26 15:58:51 2006 -0500
@@ -133,6 +133,10 @@
     Find moves and copies between m1 and m2 back to limit linkrev
     """
 
+    # avoid silly behavior for update from empty dir
+    if not m1:
+        return {}
+
     dcopies = repo.dirstate.copies()
     copy = {}
     match = {}