%p= link_to("Foo", "bar&bar".html_safe))
==> <p><a href="bar&amp;amp;amp;bar">Foo</a></p>

%p= link_to("Foo", "bar&bar")
==> <p><a href="bar&amp;amp;bar">Foo</a></p>

%p= link_to("Foo", h('bar&bar'))
==> <p><a href="bar&amp;amp;amp;bar">Foo</a></p>