Daniel, >That is not possible for SVN to determine, as it does not know *how* you are serving the repository (HTTP, HTTPS, svn+ssh, svn, >etc). $REPOS will give you the physical path to the repository, not necessarily the publicly accessible path. That not a problem. I can always prefix the protocol like file:///, http://, https:// or svn:// to the full URL.
For example if somehow svnlook can somehow return this: /var/lib/svn/projectA/PartA/tags/DEV-1.00_RC5 say in variable called URL then I do this: URL="file:///$URL"