sonic/resources/template/common/web/robots.tmpl

{{- define "common/web/robots" -}}
    {{- if .options.seo_spider_disabled -}}
User-agent: *
Disallow: /
    {{- else -}}
User-agent: *
Sitemap: {{.sitemap_xml_url}}
Sitemap: {{.sitemap_html_url}}
    {{- end -}}
{{- end -}}