This gist shows how I'm using Rouge to highlight individual lines of code. On top of the existing syntax highlighting.

I'm using Sitepress which uses markdown-rails under the hood. But this should be applicable to any application rendering markdown with Redcarpet - sub out ApplicationMarkdown as your renderer.

Append @[] when setting the language in a fenced code block to highlight lines of code. Dashes will cover the range, inclusive. Commas will highlight each line.

Examples:

```swift@[4-6]
class Person {
    private let name: String
    
    init(name: String) {
        self.name = name
    }
}
```

```ruby@[2,5]
class Person
  attr_reader :name

  def initialize(name)
    @name = name
  end
end
```