How to check out certain files from origin in a multibranch pipeline?

I’m working with a public repository and have a multibranch pipeline job that runs when pull requests are opened in the repository. I want Jenkins to checkout all changes from a pull request EXCEPT for things like Jenkinsfile, Dockerfile, and build scripts (lets say this all lives in a ci/ subdirectory).

Is there a way to have Jenkins always checkout the ci/ subdirectory from origin and ignore any changes to the subdirectory that might be included in a pull request?