get requirements tree for installed pip packages
from a list of packages merged to one requirements.txt (requires changing --write option to use append mode 'a')
cat getreqt.list | xargs -I{} getreqt --write {} && awk '!seen[$0]++' requirements.txt > reqs_unique.txt && mv reqs_unique.txt requirements.txt && pip wheel --wheel-dir=. -r requirements.txt