mercurial/help/revsets.txt

--- a/mercurial/help/revsets.txt	Fri Aug 13 13:16:34 2010 -0400
+++ b/mercurial/help/revsets.txt	Fri Aug 13 13:11:41 2010 -0300
@@ -122,6 +122,10 @@
 ``parents(set)``
   The set of all parents for all changesets in set.
 
+``present(set)``
+  An empty set, if any revision in set isn't found; otherwise,
+  all revisions in set.
+
 ``removes(pattern)``
   Changesets which remove files matching pattern.