Not so much useful in my lines, how many attempt to muster in one place all "hacks", which account for to do.
And so that at us at full HTTPS the file robots was available for robots.a txt with the correct Host Directive must be created. And this is no problem, but if you have as in my case closed access via HTTP more than completely, then how to convey to your robots robots.txt .
At the moment, I have not found anything easier than to open access only to the robot.txt on 80 port for this in section preset https for your domain adding the next:

location / {
            location = /robots.txt {
                    rewrite ^ /robots.txt break;
         }
}

Смотрите также: Redirect 301 C http to https and no-www to www