the go tool currenty has a pathology where it mistakingly claims it
can't clone a repo because it checks prefix by bytes, not by splitting
the path on slash.
Once https://github.com/golang/go/issues/15947 comes out (go1.8) then go
tools will be able to handle being provided with valid but overlapping
packages.
For now though we'll just return meta for the requested package.
Change-Id: Ie5026e7d5c1377ff7d2c2140b21f9b745af69764
