I can use the "update all local language packs" on the "Language packs" panel (langimport.php) if I have only standard languages installed. However, if I add a local language pack (not _local language folder but full language pack), the "update all local language packs" script gives an error: Cannot find component.
The local language pack has the langconfig.php with parent setting pointing to one of the installed languages. It shows in the list and the language switching menu and works fine otherwise.
Moodle 1.9 (beta 3) deletes the folder with the non-standard language !!! Moodle 1.8 at least left it alone.
Sounds like Moodle needs to be able to distinguish local and standard packs or allow us to specify which language to update as an alternative to bulk update (unless having local language packs is not supported anymore).