jekyll-theme-chirpy/_includes/post-description.html

{%- comment -%}
  Get post description or generate it from the post content.
{%- endcomment -%}

{%- capture description -%}
  {%- if post.description -%}
    {{- post.description -}}
  {%- else -%}
    {% comment %}
      Remove the line number of the code snippet.
    {% endcomment %}
    {%- assign content = post.content -%}

    {%- if content contains '<td class="rouge-gutter gl"><pre class="lineno">' -%}
      {%- assign content = content | replace: '<td class="rouge-gutter gl"><pre class="lineno">', '<!-- <td class="rouge-gutter gl"><pre class="lineno">' -%}
      {%- assign content = content | replace: '</td><td class="rouge-code">', '</td> --><td class="rouge-code">' -%}
    {%- endif -%}

    {{- content | strip_html | newline_to_br | replace: '<br />', ' ' | strip_newlines -}}
  {%- endif -%}
{%- endcapture -%}

{%- if include.json -%}
  {%- assign description = description | jsonify -%}
{%- else -%}
  {%- assign max_length = include.max_length | default: 200 -%}
  {%- assign description = description | strip | truncate: max_length -%}
{%- endif -%}

{{- description -}}