anchor.diff:  [source]
   ----
   content = '_Zen_ in the art of writing http://asciidoctor.org[AsciiDoc].'
  -html = Asciidoctor.convert content, header_footer: true, safe: 'safe'
  +html = Asciidoctor.convert content, header_footer: true, safe: :safe
   ----
   
   If you need access to the parsed document, you can split the conversion into discrete steps:
  
positive.code: // settings:
  :page-layout: base
  :idprefix:
  ifdef::env-github[:idprefix: user-content-]
  :idseparator: -
  :source-language: ruby
  :language: {source-language}
  
negative.code: [.output]
  ....
  Asciidoctor 1.5.2 [http://asciidoctor.org]
  Runtime Environment (ruby 2.2.2p95 [x86_64-linux]) (lc:UTF-8 fs:UTF-8 in:- ex:UTF-8)
  ....
  
  Asciidoctor also provides an API.
  