This is easy peasy:
TMPDIR=/var/tmp pkgrecv \ -s file:///export/home/pkgserv/reposource \ -d file:///export/home/pkgserv/repodest 'pkg:/*'
Be sure to set TMPDIR, as /tmp is normally RAM and this process can use an awful lot of disk space.
Rich Lowe has also mentioned the following tool, unsure if this is helpful:
python2.6 path/to/pkg/gate/src/util/publish/merge.py -r \ -d repo_merge \ -v true,http://localhost:13000 \ -v false,http://localhost:13001 \ debug consolidation/osnet/osnet-incorporation