title: UI Router: redirect to child state when navigating to abstract parent state
body: <p>In my music app, I have an ng-repeat on the top-level states of my app to create navigation links. One of the top-level states, called library, is abstract and has child states (which are navigable using tabs). Since I am using an ng-repeat, the abstract state has a directive of <code>ui-sref="library"</code>. However, it's not possible to navigate to an abstract parent state like that, instead I would need to write <code>ui-sref="library.albums"</code>. I am unable to do this because of the ng-repeat data coming directly from the state provider. How can I set a default child state on "library" so that whenever that state is visited, it redirects to the child?</p>
  
  <p>Here's a diagram of my setup:
  <a href="https://i.imgur.com/dWPQP63.png" rel="noreferrer"><img src="https://i.imgur.com/dWPQP63.png" alt="enter image description here"></a></p>