We added .after_reload to Sinatra::Reloader! https://github.com/sinatra/sinatra/pull/1150

Following the ticket on the old sinatra-contrib repository https://github.com/sinatra/sinatra-contrib/issues/179

require "sinatra"
require "sinatra/reloader" if development?

also_reload '/path/to/some/file'
dont_reload '/path/to/other/file'
after_reload do
  puts 'reloaded'
end