tests: let run-tests.py default to use 'sh' in $PATH instead of '/bin/sh' This makes it easier to run tests on systems that have a usable sh in the search path but not in the standard location. [ original upstream message ]

tests: add 'set -x' to the .t sh scripts in run-tests.py debug mode This makes -d output much more readable when debugging the test framework or very strange test failures. [ original upstream message ]