revset: use appropriate predicate name in error messages stable

revset: use appropriate predicate name in error messages

"extinct" and "unstable" predicates use "obsolete" implementation
internally, but own predicate name should be used in error messages of
them instead of "obsolete".

--- a/mercurial/revset.py	Thu Jul 26 23:08:34 2012 +0200
+++ b/mercurial/revset.py	Thu Jul 26 13:58:43 2012 +0900
@@ -615,7 +615,7 @@
 def extinct(repo, subset, x):
     """``extinct()``
     obsolete changeset with obsolete descendant only."""
-    getargs(x, 0, 0, _("obsolete takes no arguments"))
+    getargs(x, 0, 0, _("extinct takes no arguments"))
     extinctset = set(repo.revs('(obsolete()::) - (::(not obsolete()))'))
     return [r for r in subset if r in extinctset]
 
@@ -1406,7 +1406,7 @@
 def unstable(repo, subset, x):
     """``unstable()``
     Unstable changesets are non-obsolete with obsolete descendants."""
-    getargs(x, 0, 0, _("obsolete takes no arguments"))
+    getargs(x, 0, 0, _("unstable takes no arguments"))
     unstableset = set(repo.revs('(obsolete()::) - obsolete()'))
     return [r for r in subset if r in unstableset]