Redmine/app/views/projects/list_documents.rhtml

<div class="contextual">
<%= link_to_if_authorized l(:label_document_new), {:controller => 'projects', :action => 'add_document', :id => @project}, :class => 'icon icon-add' %>
</div>

<h2><%=l(:label_document_plural)%></h2>

<% if @documents.empty? %>
<p class="nodata"><%= l(:label_no_data) %></p>
<% end %>

<% documents = @documents.group_by {|d| d.category } %>
<% documents.each do |category, docs| %>
    <h3><%= category.name %></h3>
    <%= render :partial => 'documents/document', :collection => docs %>
<% end %>