message: Use greadlink for upgrade-test on Mac
  This fixes the incompatibility of upgrade-test on Mac
diff: set -e
  +# On Mac, use 'greadlink' instead of 'readlink'
  +if [[ "$(uname)" == "Darwin" ]]; then
  + [[ -x "$(command -v greadlink)" ]] || brew install coreutils
  + readonly READLINK="greadlink"
  +else
  + readonly READLINK="readlink"
  +fi
  readonly STABLE=${1:-stable}
  readonly PRERELEASE=${2:-$(cat VERSION)-$(git rev-parse HEAD)}
  @@ -25,19 +32,18 @@ readonly CI=${CI:-}
  readonly STABLE_TOPIC=${STABLE_TOPIC:-stable}
  readonly PRERELEASE_TOPIC=${PRERELEASE_TOPIC:-prerelease}
  readonly USE_LATEST=${USE_LATEST:-}
  -readonly FLUVIO_BIN=$(readlink -f ${FLUVIO_BIN:-"$(which fluvio)"})
  +readonly FLUVIO_BIN=$(${READLINK} -f ${FLUVIO_BIN:-"$(which fluvio)"})
  # Change to this script's directory
  -pushd "$(dirname "$(readlink -f "$0")")" > /dev/null
  +pushd "$(dirname "$(${READLINK} -f "$0")")" > /dev/null
  function cleanup() {
  echo Clean up test data
  - rm -f --verbose ./*.txt.tmp;
  - rm -f --verbose ./*.checksum;
  + rm -fv ./*.txt.tmp;
  + rm -fv ./*.checksum;
  echo Delete cluster if possible
  $FLUVIO_BIN cluster delete || true
  $FLUVIO_BIN cluster delete --sys || true
  -
  }
  # If we're in CI, we want to slow down execution
  @@ -107,7 +113,7 @@ function validate_cluster_stable() {
  # Then we produce + consume on the Stable + Stable-1 topic and validate the checksums on each of those topics
  function validate_upgrade_cluster_to_prerelease() {
  - local FLUVIO_BIN_ABS_PATH=$(readlink -f $FLUVIO_BIN)
  + local FLUVIO_BIN_ABS_PATH=$(${READLINK} -f $FLUVIO_BIN)
  local TARGET_VERSION=${PRERELEASE}
  # Change dir to get access to Helm charts
  