moving self contained subdirectories from a project to another

Lately I'm trying to move a subdirectory from one project to another, both tracked in git.

This directory is currently duplicated in two different projects and my plan was to remove it from those and make a library so it could be shared between them.

Now, the simple way would be get a scratchpad branch, prune everything but what I want, push to the library repo, make the projects use it.

There is already a script that automates this task? There are any pitfalls I'm not considering?

lu

PS: keep me on CC since I'm not subscribed