gitweb $export_ok question

Hello,

I am trying to get the gitweb $export_ok to  work. According the installation instructions:

Alternatively, you can configure gitweb to only list and allow viewing of the explicitly exported repositories, via the

GITWEB_EXPORT_OK build configuration variable (or the $export_ok variable in gitweb config file). If it evaluates to true, gitweb shows repositories only if this file exists in its object database (if directory has the magic file named $export_ok).

... I set $export_ok = "true" in my /etc/gitweb.conf file. I don't know what "file" needs to be added to a repository in order for it to show up again in gitweb. I have tried several things, like specifying the file name in /etc/gitweb.con:

$export_ok ="magic-file-name"

etc. but that doesn't seem to work.

What am I doing wrong here?