Octopress の個々のエントリに Google+ アカウントを著者情報としてリンクさせたい場合の _includes/post/author.html の記述。

author.html

{% if post.author %}
  {% assign author = post.author %}
{% elsif page.author %}
  {% assign author = page.author %}
{% else %}
  {% assign author = site.author %}
{% endif %}

{% if post.googleplus_user %}
  {% assign googleplus_user = post.googleplus_user %}
{% elsif page.googleplus_user %}
  {% assign googleplus_user = page.googleplus_user %}
{% else %}
  {% assign googleplus_user = site.googleplus_user %}
{% endif %}

{% if author %}
  <span class="byline author vcard">Posted by
    <span class="fn">
    {% if googleplus_user %}
      <a href="https://plus.google.com/{{ googleplus_user }}?rel=author">{{ author }}</a>
    {% else %}
      {{ author }}
    {% endif %}
    </span>
  </span>
{% endif %}