anchor.diff:  <div class="radio">
     <label>
       <input name="assignment[teamset_plan]" id="teamset_none" type="radio"
  -           value="none" <% if @legal_actions[:no_teams][:checked] %>checked<% end %>>
  +           value="none" <% if asgn.teamset_plan == "none" || @legal_actions[:no_teams][:checked] %>checked<% end %>>
       <strong>No teams:</strong> this assignment will be submitted individually
     </label>
   </div>
  
positive.code: <div class="radio">
    <label>
      <input name="assignment[teamset_plan]" id="teamset_use" type="radio"
             value="use" <% if @legal_actions[:use][:checked] %>checked<% end %>>
      <strong>Use existing teamset:</strong> this assignment shares a teamset with
      another one, and changes to this teamset will affect both assignments<br>
      <% if @legal_actions[:use][:existing] %>
      <input type='text' style="width: 100%;" disabled value="<%= asgn.teamset&.name %>">
      <% else %>
      <%= select_tag "assignment[teamset_source_use]",
          options_from_collection_for_select(course.teamsets, "id", "name", @legal_actions[:use][:value]),
          prompt: "Choose an existing teamset", value: @legal_actions[:use][:value],
          class: "col-sm-12" %>
      <% end %>
    </label>
  
negative.code: <div class="radio">
    <label>
      <input name="assignment[teamset_plan]" id="teamset_new" type="radio"
             value="new" <% if asgn.teamset_plan == "new" || @legal_actions[:new][:checked] %>checked<% end %>>
      <strong>New teamset:</strong> after creating this assignment, go to the Teams
      page to create a new set of teams.
      <% if @legal_actions[:new][:existing] %>
  