Just FYI, I discovered this while reading pkg_add source:
It may be possible that a package contains its dependency package in the
tar file, e.g. foo-1.7 depend on bar-4.2, and contains (as files):

foo/bin
bar-4.2.tgz

If someone keen on container packages wants to check this out, the code is
in add/perform.c, ~line 317 (snprintf(path, FILENAME_MAX, "%s/%s.tgz",
Home, p->name)), where Home is where the foo-pkg is unpacked.


 - Hubert

-- 
Hubert Feyrer <hubert.feyrer@rz.uni-regensburg.de>