redmine/app/views/members/_new_modal.html.erb

<h3 class="title"><%= l(:label_member_new) %></h3>

<%= form_for @member, :as => :membership, :url => project_memberships_path(@project), :remote => true, :method => :post do |f| %>
  <%= render :partial => 'new_form' %>
  <p class="buttons">
    <%= submit_tag l(:button_add), :id => 'member-add-submit' %>
    <%= link_to_function l(:button_cancel), "hideModal(this);" %>
  </p>
<% end %>