Sorry, at the moment this is not possible with the cli. The only thing you could do at the moment is a ugly workaround. You could install the scm-script-plugin and execute the following groovy script with curl or something similar:
import javax.servlet.http.HttpServletRequest;
import de.triology.scm.plugins.groupmanager.GroupManagerResource;
def request = injector.getInstance(HttpServletRequest.class);
String groupName = request.getParameter("group");
String managerName = request.getParameter("manager");
if ( groupName == null || managerName == null ){
throw new IllegalArgumentException( "parameter group and manager are required" );
};
def groupManager = injector.getInstance(GroupManagerResource.class);
def group = null;
for (def g : groupManager.getAll().getEntity().getEntity()){
if (groupName.equals(g.getName())){
group = g;
break;
};
};
if (group == null){
throw new IllegalArgumentException( "group not found" );
};
if (!group.addManager(managerName)){
throw new IllegalStateException("could not add manager to group");
};
if (groupManager.update(null, groupName, group).getStatus() != 204){
throw new IllegalStateException("group update failed");
}