How update Node-Red nodes?

A simple question.
When I update nodes in Node-Red (e.g. Palette manager),
are the new files merged with old files or old files are deleted first and then new files are copied ?
What action is made, if the old file is deleted in new version ?
Thanks for answer.

Updating a module completely replaces the old version with the new version. It doesn't leave you with some mix of both.