how to set https for naked domain?

Solution 1:

Well first of all I had to generate ssl certificate for naked domain - digrin.com. I set temporarily A tag for digrin.com to openshift's ip and generated ssl certificate.
Now we have working certificate, but since A tag for digrin can not be set permanently, domain registrant must support naked domain redirect. More on this you can read here -> if you registrant does not support it, move to cloudfront (I will test cloudfront if my registrant will not add this feature within few months and will update this answer).

Solution 2:

If you are looking for a free (1 domain) service that redirects naked domains with valid SSL certificates. I moved from wwwizer to nakedssl to redirect to an Opensift server and it works fine.