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