Allow searching by negated favgroup: metatag

app/logical/post_query_builder.rb

@@ -312,6 +312,14 @@ class PostQueryBuilder
       relation = relation.order("position(' '||posts.id||' ' in ' '||(select post_ids from pools where id = #{pool_id})||' ')")
     end
 
+    if q[:favgroup_neg].present?
+      favgroup_id = q[:favgroup_neg].to_i
+      favgroup = FavoriteGroup.where("favorite_groups.id = ?", favgroup_id).first
+      if favgroup
+        relation = relation.where("posts.id NOT in (?)", favgroup.post_id_array)
+      end
+    end
+
     if q[:favgroup].present?
       favgroup_id = q[:favgroup].to_i
       favgroup = FavoriteGroup.where("favorite_groups.id = ?", favgroup_id).first