asciinema.org/app/helpers/application_helper.rb

module ApplicationHelper
  def twitter_auth_path
    "/auth/twitter"
  end

  def github_auth_path
    "/auth/github"
  end

  def default_avatar_url
    image_path "default_avatar.png"
  end

  def avatar_img(user)
    nickname =  "~#{user.nickname}"
    image_tag user.avatar_url || default_avatar_url,
      :title => nickname, :alt => nickname, :class => "avatar"
  end
end