Destroying a terraform state can't always create an empty state, as
outputs and the root module may remain. Use HasResources to warn about
deleting an environment with resources.
In order to operate in parity with other commands, the env command
should take a path argument to locate the configuration.
This however introduces the issue of a possible name conflict between a
path and subcommand, or printing an incorrect current environment for
the bare `env` command. In favor of simplicity this removes the current
env output and only prints usage when no subcommand is provided.