Use `getopt` to process options

[bbros-dev]

Feeding back a more radical change than the prior suggestions in PR #8 and issue #9.

What I now have in my template.sh:

From memory, I iterated from this blog source and this gist.

function parse_params() {
  # -allow a command to fail with !’s side effect on errexit
  # -use return value from ${PIPESTATUS[0]}, because ! hosed $?
  ! getopt --test > /dev/null 
  if [[ ${PIPESTATUS[0]} -ne 4 ]]; then
      script_exit 'I’m sorry, `getopt --test` failed in this environment.' 2
  fi

  OPTIONS=chno:v
  LONGOPTS=cron,help,no-color,output:,verbose

  # -regarding ! and PIPESTATUS see above
  # -temporarily store output to be able to check for errors
  # -activate quoting/enhanced mode (e.g. by writing out “--options”)
  # -pass arguments only via   -- "$@"   to separate them correctly
  ! PARSED=$(getopt --options=$OPTIONS --longoptions=$LONGOPTS --name "$0" -- "$@")
  if [[ ${PIPESTATUS[0]} -ne 0 ]]; then
      # e.g. return value is 1
      #  then getopt has complained about wrong arguments to stdout
      script_exit "Argument error" 2
  fi
  # read getopt’s output this way to handle the quoting right:
  eval set -- "$PARSED"

  local param
...