Prevent WordPress updates from overriding custom language translations?

Question

my site's language is persian and persian is a right-to-left language. Wordpress has a default installation package for this lang but for some cases like very bad translation for dashboard or default rtl style for everything (that is really annoying for theming) i installed original Wordpress in English and then use a custom language file for my theme. everything is ok but as you know for doing this i should set following line in wp-config.php file for running my theme in persian:

define('WPLANG', 'fa-IR');

but with changing this line of code in wp-config Wordpress think that i use persian version of Wordpress and say your Wordpress version is not update!

WordPress 3.9.2 is available! Please update now.

with changing the line to its default, update message disappears! if i click the update button Wordpress installs persian package, something that i really don't want to! the only solution is change the line to its default, update wordpress and change it back to "fa-IR"! is there a better approach to do this? is there a better way? what if one of users accidentally click on update button? thanks.

Answer 1

Modify your installation such that your custom Farsi language files are associated with a non-standard WPLANG value. For example, instead of the standard 'fa_IR', maybe try something non-standard like 'farsi_IR' (or even 'myCustomFarsi_IR').

This way, when new WordPress versions are released for the "official" Farsi version, you will no longer get updated.