diff -r f1895785c79e -r cde6818e082a mercurial/revlog.py
--- a/mercurial/revlog.py	Thu Sep 08 00:13:52 2005 -0700
+++ b/mercurial/revlog.py	Thu Sep 08 01:27:25 2005 -0700
@@ -604,8 +604,8 @@
             link = linkmapper(cs)
             if node in self.nodemap:
                 # this can happen if two branches make the same change
-                if unique:
-                    raise RevlogError("already have %s" % hex(node[:4]))
+                # if unique:
+                #    raise RevlogError("already have %s" % hex(node[:4]))
                 chain = node
                 continue
             delta = chunk[80:]