[TYPO3-install] Typo3 with simulateStatic in a subdirectory

[Levente J. Dobszay]

Hi folks!

Facing a nervous breakdown I ask you for your help!

I have installed Typo3 in a subdirectory of my web root (htdocs/cms/). 
simulateStatic works quite fine, accessing my site calling 
http://www.mySite.com/cms/.

Now I would like to make my website only accessible calling 
http://www.mySite.com/. All invalid URLs (404) as well as any direct call of 
http://www.mySite.com/cms/... (except calling the backend) should be 
redirected to http://www.mySite.com/. I.e. no visitor should ever see in 
which subdirectory my typo3 is installed (due to security reasons).

What exactly has to be defined in which .htaccess file (/htdocs/.htaccess 
and /htdocs/cms/.htaccess) in order to make this work as required?

Is this possible with Typo3 anyway? If yes, does this have a major impact on 
the performance of the Apache server?

Regards,
Levente