ftp-deploy: Delete everything except one folder while uploading

[SanujMID]

I am using ftp push via ftp-deploy: https://bitbucket.org/atlassian/ftp-deploy/src/master/

I have configured it so that everything get deployed from my webpack's dist(build) folder.
I have one particular folder on server, whose contents get deployed from other pipeline from another project.

Ho can I prevent this pipeline to delete that particular folder called app.

[SanujMID]

Meanwhile we get a proper way via config in ftp-deploy, here is a workaround.

I used two different deployment steps: 

1 automatic on every push, Update to environment, using delete flag as false.

2 manual, Complete deployment to environment, using delete flag as true.

Although this is working for me right now, but we would definitely want an option to avoid deleting a specified folder but delete everything else.