Fixup the `Subgroups` call

groups.go

@@ -269,11 +269,18 @@ func (s *GroupsService) ListGroupProjects(gid interface{}, opt *ListGroupProject
 	return p, resp, err
 }
 
+// ListSubgroupsOptions represents the available ListSubgroupsOptions()
+// options.
+//
+// GitLab API docs:
+// https://docs.gitlab.com/ce/api/groups.html#list-a-groups-s-subgroups
+type ListSubgroupsOptions ListGroupsOptions
+
 // ListSubgroups gets a list of subgroups for a given project.
 //
 // GitLab API docs:
-// https://docs.gitlab.com/ce/api/groups.html#list-project-groups
-func (s *GroupsService) ListSubgroups(gid interface{}, opt *ListGroupsOptions, options ...OptionFunc) ([]*Group, *Response, error) {
+// https://docs.gitlab.com/ce/api/groups.html#list-a-groups-s-subgroups
+func (s *GroupsService) ListSubgroups(gid interface{}, opt *ListSubgroupsOptions, options ...OptionFunc) ([]*Group, *Response, error) {
 	group, err := parseID(gid)
 	if err != nil {
 		return nil, nil, err