merge I18n keys from multiple files and write in a single file

en.yml

en:
  app:
    my_key: ..

it.yml

it:
  app:
    my_key: ..

merge_i18n_keys.rb

def transform_hash(original, options={}, &block)
  original.inject({}) do |result, (key,value)|
    value = if (options[:deep] && Hash === value) 
              transform_hash(value, options, &block)
            else 
              value
            end
    block.call(result,key,value)
    result
  end
end

I18n.backend.send(:init_translations)
translations = I18n.backend.send(:translations)
I18n.available_locales.each do |locale|
  locale_hash = translations[locale][:app]
  locale_translations = transform_hash(locale_hash, :deep => true) { |hash, key, value| hash[key.to_s] = value }
  File.open("merged_#{locale}.yml", 'w+') { |f| f.write(locale_translations.to_yaml)}
end

In this case I need merging the locales key coming from the main app with keys coming from an engine. So all translations can be handled in one single file.
To avoid merging keys coming from various gem just add the app namespace to locale files you want to merge. Then I need to deep transform the keys of the hash in string for the yml conversion.

used on rails 4.2.8