server {
    server_name site.com;
    return 301 https://$host$request_uri;
}

server {
    listen 443 ssl;
    server_name site.com;
    root /var/sites/_site.com/www;

    ...
}

# Other sites/subdomains
include sites-includes/site.com-*.conf;

server {
    server_name files.site.com;
    return 301 https://$host$request_uri;
}

server {
    listen 443 ssl;
    server_name files.site.com;
    root /var/sites/_site.com/files;

    ...

    # Visible index
    autoindex on;
}