The ports-mgmt/porttools program is part of the Ports Collection.
port is the front-end script, which can help you simplify the testing job. Whenever you want to test a new port or update an existing one, you can use port test to test your port, including the portlint checking. This command also detects and lists any files that are not listed in pkg-plist. See the following example:
# port test /usr/ports/net/csup