Redmine/app/views/attachments/_form.html.erb

<span id="attachments_fields">
<% if defined?(container) && container && container.saved_attachments %>
  <% container.saved_attachments.each_with_index do |attachment, i| %>
    <span id="attachments_p<%= i %>">
      <%= text_field_tag("attachments[p#{i}][filename]", attachment.filename, :class => 'filename') +
          text_field_tag("attachments[p#{i}][description]", attachment.description, :maxlength => 255, :placeholder => l(:label_optional_description), :class => 'description') +
          link_to('&nbsp;'.html_safe, attachment_path(attachment, :attachment_id => "p#{i}", :format => 'js'), :method => 'delete', :remote => true, :class => 'remove-upload') %>
      <%= hidden_field_tag "attachments[p#{i}][token]", "#{attachment.token}" %>
    </span>
  <% end %>
<% end %>
</span>
<span class="add_attachment">
<%= file_field_tag 'attachments[dummy][file]',
      :id => nil,
      :class => 'file_selector',
      :multiple => true,
      :onchange => 'addInputFiles(this);',
      :data => {
        :max_file_size => Setting.attachment_max_size.to_i.kilobytes,
        :max_file_size_message => l(:error_attachment_too_big, :max_size => number_to_human_size(Setting.attachment_max_size.to_i.kilobytes)),
        :max_concurrent_uploads => Redmine::Configuration['max_concurrent_ajax_uploads'].to_i,
        :upload_path => uploads_path(:format => 'js'),
        :description_placeholder => l(:label_optional_description)
      } %>
(<%= l(:label_max_size) %>: <%= number_to_human_size(Setting.attachment_max_size.to_i.kilobytes) %>)
</span>

<% content_for :header_tags do %>
  <%= javascript_include_tag 'attachments' %>
<% end %>