These functions allow a Named type to be combined with a tag or a
digest. WithTag will replace the ImageReference function in
github.com/docker/docker/utils as the Docker Engine transitions to the
reference package.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
In order to support valid hostnames as name components, supporting repeated dash was added.
Additionally double underscore is now allowed as a separator to loosen the restriction for previously supported names.
Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)