app/views/devise/sessions/new.html.erb
<h2><%= I18n.t 'user.login' %></h2>
<%= form_for(resource, as: resource_name, url: session_path(resource_name)) do |f| %>
<div class="field">
<%= f.label :username_or_email %><br />
<%= f.text_field :login, autofocus: true, class: 'form-control' %>
</div><br/>
<div class="field">
<%= f.label :password %><br />
<%= f.password_field :password, autocomplete: "off", class: 'form-control' %>
</div><br/>
<% if devise_mapping.rememberable? -%>
<div class="field">
<%= f.check_box :remember_me %>
<%= f.label :remember_me %>
</div>
<% end %>
<div class="actions">
<%= f.submit t('.sign_in'), class:"btn btn-primary" %>
</div>
<% end %>
<hr/>
<%= render "devise/shared/links" %>