given the length of this line, we should probably do:
```ruby
<% auto_complete_box = autocomplete_field_tag 'fake_reserver_id', User.find(cart.reserver_id)  == current_user ? '' : User.find(cart.reserver_id).render_name, autocomplete_user_last_name_reservations_path, :size => 30, :placeholder => "Enter a name or login", :class => 'submittable span2' %>

<% new_user_button =  link_to sanitize("<i class=\"icon-plus\"></i>"), '#userModal', :class => 'btn', :id => 'modal', :rel => 'tooltip', :title => 'New Reserver', :"data-toggle" => 'modal' %>

<%= auto_complete_box%><%= new_user_button %>
```

But maybe use helper methods and/or an if statement to choose what the new_user_button does based on the setting to use LDAP for new user creation.