anchor.diff: +- var isArticle = contains(collection, 'articles');
  +- var isWork = contains(collection, 'work');
  +- var isTalk = contains(collection, 'talks');
  +- var isCollection = isArticle || isWork || isTalk;
   doctype html
   html(lang="en")
     head
  
positive.code:     meta(
        name="author"
        content=site.author)
      - var titles = hide_title ? [] : [title];
      if client
        - titles.push(client);
  
negative.code:               - var cn = { 'Nav-link--active': isSelf || isInCollection };
                li.Nav-item
                  a.Nav-link(href=url, class=cn)= page.title
      main.Article(role="main")
        .Article-section
          h1.Article-h1= title
  