Define hookable API in module that’s included, this way other clients can include a module that overrides those hooks. Because including modules inserts the methods in the ancestor lookup chain (i.e. the power of Ruby), this allows the use of super etc.

gistfile1.rb

module API
  def execute(command)
    puts command
  end
end

class Downloader
  include API

  def download!
    execute('git clone URL')
  end
end

d = Downloader.new
d.download!

module APIOverrides
  def execute(command)
    puts "\nExecuting:"
    super
  end
end

class Downloader
  include APIOverrides
end

d.download!