allow forum posts to be searched by category (#1720)

app/models/forum_post.rb

@@ -56,6 +56,10 @@ class ForumPost < ActiveRecord::Base
         q = q.creator_name(params[:creator_name].tr(" ", "_"))
       end
 
+      if params[:topic_category_id].present?
+        q = q.joins(:topic).where("forum_topics.category_id = ?", params[:topic_category_id].to_i)
+      end
+
       q
     end
   end

app/views/forum_posts/search.html.erb

@@ -5,6 +5,10 @@
       <%= search_field "topic_title_matches", :label => "Title" %>
       <%= search_field "body_matches", :label => "Body" %>
       <%= search_field "creator_name", :label => "Author" %>
+      <div class="input">
+        <label for="search_topic_category_id">Category</label>
+        <%= select "search", "topic_category_id", ForumTopic::CATEGORIES.invert.to_a, :include_blank => true %>
+      </div>
       <%= submit_tag "Search" %>
     <% end %>
   </div>