title: How to find the reblog source from the Tumblr API
body: <p>Using Tumblr API v2, I have a list of photo posts in JSON using the /posts API call.</p>
  
  <p>For each post I would like to know which user the post was reblogged from (if any), in the same way that Tumblr shows which user a post was reblogged from.</p>
  
  <p>It is possible to get the source_url or source_title from the /posts reply but that is not the last reblogger - that appears to be the initial source.</p>
  
  <p>Any ideas?</p>