diff -r 28ed1c4511ce -r 75f4180509a4 mercurial/context.py
--- a/mercurial/context.py	Thu Jun 07 19:21:59 2012 +0200
+++ b/mercurial/context.py	Wed Jun 06 01:56:58 2012 +0200
@@ -230,6 +230,10 @@
         for d in self._repo.changelog.descendants([self._rev]):
             yield changectx(self._repo, d)
 
+    def obsolete(self):
+        """True if the changeset is obsolete"""
+        return self.node() in self._repo.obsstore.obsoleted
+
     def _fileinfo(self, path):
         if '_manifest' in self.__dict__:
             try: