bookmarks: verify switching bookmarks works properly

tests/test-bookmarks-current.t

@@ -66,6 +66,17 b' list bookmarks'
    * Y                         0:719295282060
      Z                         -1:000000000000
 
+Verify that switching to Z updates the current bookmark:
+  $ hg update Z
+  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  $ hg bookmark
+     Y                         0:719295282060
+   * Z                         -1:000000000000
+
+Switch back to Y for the remaining tests in this file:
+  $ hg update Y
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
 delete bookmarks
 
   $ hg bookmark -d Y