--- a/hgext/evolve.py	Mon Jun 30 10:27:15 2014 -0400
+++ b/hgext/evolve.py	Mon Jun 30 10:25:08 2014 -0400
@@ -2099,6 +2099,11 @@
         revs = ()
     if not revs:
         raise util.Abort(_('no revisions specified'))
+
+    if len(revs) == 1:
+        ui.write_err(_('single revision specified, nothing to fold\n'))
+        return 1
+
     roots = repo.revs('roots(%ld)', revs)
     if len(roots) > 1:
         raise util.Abort("set has multiple roots")