* It is more performant given now we process all the diff file instead
  of processing line by line.
* Multiline comments are highlighted correctly.

Closes #4295

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

A limited number of pages have defined their own descriptions, but
otherwise we default to the Project's description (if `@project` is
set), or the old `brand_title` fallback.

The image will either be the uploaded project icon (never a generated
one), the user's uploaded icon or Gravatar, or, finally, the GitLab
logo.

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

`runners_registration_token` now creates a new token if it is blank.