cache_digests dependency dump rake task updated for Rails 4

cache_digests.rake

# The functionality from the cache_digests gem (https://github.com/rails/cache_digests) 
# has been merged into actionpack for Rails 4, 
# but the handy rake task to dump the template dependency hierarchy for a given template
# to the console didn't. Here's the rake task from DHH's cache_digests project tree, updated
# for ActionView in Rails 4. Copy it to your project's lib/tasks directory as "cache_digests.rake"

namespace :cache_digests do
  desc 'Lookup nested dependencies for TEMPLATE (like messages/show or comments/_comment.html)'
  task :nested_dependencies => :environment do
    raise 'You must provide TEMPLATE for the task to run' unless ENV['TEMPLATE'].present?
    template, format = ENV['TEMPLATE'].split(".")
    format ||= :html
    puts JSON.pretty_generate ActionView::Digestor.new(template, format, ApplicationController.new.lookup_context).nested_dependencies
  end

  desc 'Lookup first-level dependencies for TEMPLATE (like messages/show or comments/_comment.html)'
  task :dependencies => :environment do
    raise 'You must provide TEMPLATE for the task to run' unless ENV['TEMPLATE'].present?
    template, format = ENV['TEMPLATE'].split(".")
    format ||= :html
    puts JSON.pretty_generate ActionView::Digestor.new(template, format, ApplicationController.new.lookup_context).dependencies
  end
end