hi,
I had a problem to integrate
fresh cook .ini language files and
old .ini translated earlier,
so I made script for that works like this:

you have 2 language files:
old one - translated
and new one - not translated

you want to merge that 2 files to have only language keys form new file with:
all corresponding old translations
and all new keys - not translated


you can use it here:
How to update/merge Joomla language files?