DOWNLOAD_COMMAND=""
function set_download_command () {
  # Try curl.
  if command -v curl > /dev/null; then
    if curl --version | grep Protocols  | grep https > /dev/null; then
      DOWNLOAD_COMMAND="curl -fLSs --retry 5 --retry-delay 1 --retry-connrefused"
      return
    fi
    echo curl does not support https, will try wget for downloading files.
  else
    echo curl is not installed, will try wget for downloading files.
  fi

  # Try wget.

function log() {
  echo -e "$(date -u '+%Y-%m-%dT%H:%M:%S.%NZ')\t$*"
}

function retry() {
  local n=1
  local max=5
  local delay=5
  while true; do
    "$@" && break
    if [[ $n -lt $max ]]; then
      ((n++))
      log "Command failed. Attempt $n/$max:"
      sleep $delay;
    else
      log "The command has failed after $n attempts."  >&2
      return 2
    fi
  done
}

#
# Separately, if TFCI is set *and* there are also additional TFCI_ variables
# set in the shell environment, those variables will be restored after the
# TFCI env has been loaded. This is useful for e.g. on-demand "generic" jobs
# where the user may wish to change just one option.
if [[ -z "${TFCI:-}" ]]; then
  echo '==TFCI==: The $TFCI variable is not set. This is fine as long as you'

DOWNLOAD_COMMAND=""
function set_download_command () {
  # Try curl.
  if command -v curl > /dev/null; then
    if curl --version | grep Protocols  | grep https > /dev/null; then
      DOWNLOAD_COMMAND="curl -fLSs --retry 5 --retry-delay 1 --retry-connrefused"
      return
    fi
    echo curl does not support https, will try wget for downloading files.
  else
    echo curl is not installed, will try wget for downloading files.
  fi

  # Try wget.