Fix #537 - opengraph description should display spoiler text when present

app/views/stream_entries/show.html.haml

@@ -5,6 +5,10 @@
   %meta{ property: 'og:site_name', content: 'Mastodon' }/
   %meta{ property: 'og:type', content: 'article' }/
   %meta{ property: 'og:title', content: "#{@account.username} on #{Rails.configuration.x.local_domain}" }/
+
+  - if @stream_entry.activity.is_a?(Status) && !@stream_entry.activity.spoiler_text.blank?
+    %meta{ property: 'og:description', content: @stream_entry.activity.spoiler_text }/
+  - else
     %meta{ property: 'og:description', content: @stream_entry.activity.content }/
 
   - if @stream_entry.activity.is_a?(Status) && @stream_entry.activity.media_attachments.size > 0