summary: test that current bookmark isn't shown

This exposes the current behavior in a test. A later change will make
summary show when the active bookmark has moved out from under us.

tests/test-bookmarks.t

@@ -467,6 +467,13 b' create bundle with two heads'
 
 update to current bookmark if it's not the parent
 
+  $ hg summary
+  parent: 2:db815d6d32e6 
+   2
+  branch: default
+  bookmarks: Y x  y
+  commit: 1 added, 1 unknown (new branch head)
+  update: 2 new changesets (update)
   $ hg update
   updating to active bookmark Z
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved