Currently I know three ways managing plugin translations, notably when their plugin:
- Commit the plugin language files (which were installed by WordPress plugin install instead composer)
- Install plugin translation composer packages
(Install&Update wordpress languages with composer) - only available for a small subset of plugins.
- (Currently best approach) Install the language files using the wp cli (using a Trellis hook Adding wp language files on deploy).
Also the WordPress core translations have to be updated from time to time -
how to properly version them.