# HG changeset patch
# User mpm@selenic.com
# Date 1116358826 28800
# Node ID b2e3528115da1f6c923a39771bf5946f6ae96260
# Parent  9fd5b35cfc45235a05f0b82bd7a87ed3ab9f9dc4
More useful message on broken addgroup chain



diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -411,6 +411,8 @@ class revlog:
 
         # retrieve the parent revision of the delta chain
         chain = data[24:44]
+        if not chain in self.nodemap:
+            raise "unknown base %s" % short(chain[:4])
 
         # track the base of the current delta log
         r = self.count()