I noticed in the static deltas tests, there were some tests that
should have been under `-o pipefail` to ensure we properly propagate
errors.
There were a few places where we were referencing undefined variables.
Overall, this is clearly a good idea IMO.
First, git doesn't do this, and whatever Linus thinks is right or
something.
Second specifically to OSTree, it's quite common to not have
intermediate commits. If one wants to reset a ref in order to prune
data after a deployment, the parentage check will fail.
Closes: https://github.com/GNOME/ostree/pull/87
Colin Walters