The file RELEASE_URL in this directory is used by the rsync infrastructure at the MacPorts server to control the tag from which "released" code is provided, ultimately at rsync://rsync.macports.org/macports/release/base/. The script handling that operation checks out from svn the code tagged by the contents of the RELEASE_URL file and makes that code available via rsync. The script is in svn at base/portmgr/mprsyncup.