I was going to fix a bug in the static deltas code and I noticed
we were missing `pull-test.sh` coverage for bareuseronly 🙈.
Obviously fixing this requires duplicating some of the bits we have in
`basic-test.sh`; need to hoist that into `libtest.sh`. For now though let's get
the coverage.
Closes: #1270
Approved by: jlebon
Colin Walters