properly resolve the current git revision
properly resolve the current git revision

Fixes issue where pull requests, e.g., #1131, are missing out on the
cuckoo/data-private/.cwd file as there is no package reference, failing
the unit tests on Travis CI.

cuckoobox/cuckoo,cuckoobox/cuckoo,cuckoobox/cuckoo,cuckoobox/cuckoo,cuckoobox/cuckoo