The `set -euo pipefail` shouldn't be controversial.
The `set -x` bit is more debatable because it makes
the output more verbose but I find it helpful right
now as I comb through all sorts of details as part of
https://github.com/coreos/fedora-coreos-tracker/issues/1861.
If we care about less verbose output, I'd prefer we keep `-x` but
switched to having rpm-ostree buffer postprocess output and only dump it
if it fails.
The "tiers" nomenclature ended up being unhelpful since
we introduced "tier-x" which is between tier-0 and tier-1.
We also never exposed the tier naming outside of our source
code. In preparation for doing so, rename to tier-0 to
"minimal" which is a bit more descriptive.
Renaming the other images will follow.
Signed-off-by: Colin Walters <walters@verbum.org>