title: Rails3 + Devise : prevent password validation when updating
body: <p>I've looking for a way to allow users to change their settings (User model) without having to change their password (they still have to enter their current password). Devise out of the box seems to allow this, but when you remove the validatable module and setup custom validations, it seems you need to work around a bit.</p>
  
  <p>I have setup the following validation in my user model : </p>
  
  <pre><code>validates :password, length: { in: 6..128 }
  </code></pre>
  
  <p>When signing up, user is required to specify his password (which is what I expect). When updating settings, though, if I leave password blank it raises an error to the user that says password must be at least 6 characters. </p>
  
  <p>How can I work around this without having to change the way Devise works or having to implement a custom controller of some sort ?</p>