Standardise shell
fix #425 (closed) except for the "reduce duplication" part. I don't see that much opportunities for reuse, except the set -euo pipefail
and getting the top level directory, but if someone wants to elaborate I can do some of it too.
I did not modify tests/chutney/arti-bench
because I don't understand where it's getting $CHUTNEY_PATH
from.
While testing each script, I noticed some READMEs where outdated, so I made a commit for that.