I'm requiring to rewrite www.domain.com/newsite/ as www.domain.com/, essentially I'm carrying this out just just in case the brand new site has some unpredicted problem, I'm able to easily roll-to the initial by editing the .htaccess file...

Do this rule:

RewriteRule !^newsite/ newsite%{REQUEST_URI}

It'll rewrite any request that doesn't begin with /newsite/ to /newsite/.