anchor.diff:    Each hero in the heroes view should have a delete button.
   
     Add the following button element to the heroes component HTML, after the hero
  -  name in the repeated `<li>` tag.
  +  name in the repeated `<li>` element.
   
   +makeExcerpt('src/app/heroes.component.html', 'delete', '')
   
  
positive.code:   ### Add the ability to save hero details
  
    At the end of the hero detail template, add a save button with a `click` event
    binding that invokes a new component method named `save`.
  
  +makeExcerpt('src/app/hero-detail.component.html', 'save')
  
  :marked
    Add the following `save` method, which persists hero name changes using the hero service
    `update` method and then navigates back to the previous view.
  
  +makeExcerpt('src/app/hero-detail.component.ts', 'save')
  
  :marked
    ### Add a hero service _update_ method
  
    The overall structure of the `update` method is similar to that of
    `getHeroes`, but it uses an HTTP `put()` to persist server-side changes.
  
  
  +makeExcerpt('src/app/hero.service.ts', 'update')
  
negative.code:     ## Keep the app transpiling and running
      Enter the following command in the terminal window:
  
    code-example(language="sh" class="code-shell").
      npm start
  
    :marked
      This command runs the TypeScript compiler in "watch mode", recompiling automatically when the code changes.
      The command simultaneously launches the app in a browser and refreshes the browser when the code changes.
  
  :marked
    You can keep building the Tour of Heroes without pausing to recompile or refresh the browser.
  
  .l-main-section#http-providers
  