anchor.diff:  
   [source]
   ----
  -content = '_Zen_ in the art of writing http://asciidoctor.org[AsciiDoc].', safe: :safe
  +content = '_Zen_ in the art of writing http://asciidoctor.org[AsciiDoc].', safe: 'safe'
   html_document = Asciidoctor.convert content, header_footer: true
   ----
   
  
positive.code: 
  == The Big Picture
  
  image::{screenshot-img}[Preview of AsciiDoc source and corresponding rendered HTML]
  
  == AsciiDoc Processing
  
  Asciidoctor reads and parses text written in the AsciiDoc syntax, then feeds the parse tree into a set of built-in templates to produce HTML 5, DocBook 5 or DocBook 4.5.
  You have the option of using your own {tilt-uri}[Tilt]-supported templates to customize the generated output or to convert AsciiDoc to additional formats.
  
  NOTE: Asciidoctor is a drop-in replacement for the original AsciiDoc Python processor.
  The project has {tests-uri}[> 1,500 tests] to ensure compatibility with the AsciiDoc syntax.
  
  In addition to the standard AsciiDoc syntax, Asciidoctor recognizes additional markup and formatting options, such as font-based icons (e.g., [x-]`icon:fire[]`) and UI elements (e.g., [x-]`button:[Save]`).
  Asciidoctor also offers a modern, responsive theme based on {foundation-uri}[Foundation] to style the HTML output.
  
  == Requirements
  
  
negative.code: * Opal (JavaScript)
  
  We welcome your help testing Asciidoctor on other platforms as well.
  Refer to <<{idprefix}contributing,Contributing>> to learn how to get involved.
  
  == Installation
  
  Asciidoctor can be installed using (a) the `gem install` command, (b) Bundler or (c) package managers for popular Linux distributions.
  
  TIP: The benefit of using a Linux package manager to install the gem is that it handles installing Ruby and RubyGems if they're not already installed on your machine.
  The drawback is that package may not be available immediately after the release of the RubyGem.
  If you need the latest version, you can always fallback to using the `gem` command.
  
  === (a) gem install
  
  Open a terminal and type: (without the leading `$`)
  
   $ gem install asciidoctor
  
  If you want to install a pre-release version (e.g., a release candidate), use:
  
   $ gem install asciidoctor --pre
  
  .Upgrading your installation
  [TIP]
  ====
  If you have an earlier version of Asciidoctor installed, you can update it using:
  
   $ gem upgrade asciidoctor
  
  If you install a new version of the gem using `gem install` instead of gem update, you'll have multiple versions installed.
  If that's the case, use the following gem command to remove the old versions:
  
   $ gem cleanup asciidoctor
  ====
  
  === (b) Bundler
  
  . Create a Gemfile in the root folder of your project (or the current directory)
  . Add the `asciidoctor` gem to your Gemfile as follows:
  