Purge empty directories that don't exist locally on SFTP upload

[madwort]

The (rather complicated) scenario

• I have an Amazon EC2 AMI built with a bunch of cookbooks required for production deployment
• I am using this AMI as a base to do kitchen tests, for CI
• the kitchen tests require slightly fewer cookbooks
• kitchen-sync deletes the files from the excess cookbooks, but not the empty directories
• test-kitchen gives me this ominous looking (but completely harmless) warning:

[2019-11-08T17:26:58+00:00] WARN: Cookbook 'compat_resource' is empty or entirely chefignored at /var/tmp/chef/cookbooks/compat_resource

kitchen-sync behaviour

remote directory list before:

cookbook1/files
cookbook2/files

local directory list before:

cookbook1/files

CURRENT remote directory list after:

cookbook1/files
cookbook2/

EXPECTED remote directory list after:

cookbook1/files