title: Rails :overwrite_params with nested parameters
body: <p>I'm using the :overwrite_params option in link_to helper. But I have problems overwriting nested parameters values. Here some code:</p>
  
  <p>With:</p>
  
  <pre><code>link_to book_item.editorial, :overwrite_params  =&gt; {:filter =&gt; {[editorials.id] =&gt; book_item.editorial.id.to_s}}
  </code></pre>
  
  <p>The complete <code>params[:filter]</code> value is replaced (ie. I lost <code>params[:filter][:author]</code> value)</p>
  
  <p>If I use:</p>
  
  <pre><code>link_to book_item.editorial, :overwrite_params  =&gt; {'filter[editorials.id]' =&gt; book_item.editorial.id.to_s} 
  </code></pre>
  
  <p>I don't lost values, but if <code>params[:filter][:editorials]</code> exists in the url, another <code>params[:filter][:editorials]</code> is attached, so I don't get any overwrite.</p>
  
  <p>Any help?</p>
  
  <p>Thanks in advance.</p>