Comment 1 for bug 1186264

This is now available as the 'help-tool' command:

$ juju help-tool config-get
Usage: config-get [options] [<key>]

Summary:
print service configuration

Options:
-a, --all (= false)
    print all keys
--format (= smart)
    Specify output format (json|smart|yaml)
-o, --output (= "")
    Specify an output file

Details:
When no <key> is supplied, all keys with values or defaults are printed. If
--all is set, all known keys are printed; those without defaults or values are
reported as null. <key> and --all are mutually exclusive.