app/themes/hugo-theme-stack/layouts/shortcodes/quote.html

<blockquote>
    <p>{{ .Inner | markdownify }}</p>
    {{- if or (.Get "author") (.Get "source") -}}
    <span class="cite"><span>― </span>
        {{- if .Get "author" -}}
        <span>
            {{- .Get "author" -}}{{- if .Get "source" -}}, {{ end -}}
        </span>
        {{- end -}}
        {{- with .Get "url" -}}<a href="{{ . }}">{{- end -}}
            <cite>{{ .Get "source" }}</cite>
        {{- if .Get "url" -}}</a>{{- end -}}
    </span>
    {{- end -}}
</blockquote>