app/views/sessions/new.html.erb
<% title = t(:sign_in) %>
<% content_for(:title) { title } %>
<div class="page-header">
<h1><%= title %></h1>
</div>
<%= form_for(@sign_in_form, url: :sessions, html: { class: 'form-horizontal' }) do |f| %>
<div class="control-group">
<%= f.label :username, class: 'control-label' %>
<div class="controls">
<%= f.text_field :username, required: true, autofocus: true %>
</div>
</div>
<div class="control-group">
<%= f.label :password, class: 'control-label' %>
<div class="controls">
<%= f.password_field :password, required: true %>
</div>
</div>
<div class="control-group">
<div class="controls">
<%= f.submit t("sign_in"), class: 'btn btn-primary' %>
</div>
</div>
<% end %>