knife-ec2 0.14.0 release notes:

This release of knife-ec2 contains minor bug fixes.

Features added in knife-ec2 0.14.0

Added support to flavor list in json format using --format json option.
--security-group-id option to specify security groups for the server. This opiton can be used multiple times when specifying multiple security groups. e.g. -g sg-e985168d -g sg-e7f06383 -g sg-ec1b7e88.

Note: The --security-group-ids option will be removed in a future release. Use the new --security-group-id option.