POSIX shell: support long options by converting them to short options

longopts2getopts.sh

# a refinement of https://stackoverflow.com/a/5255468/519360
# see also my non-translating version at https://stackoverflow.com/a/28466267/519360

# translate long options to short
reset=true
for arg in "$@"
do
    if [ -n "$reset" ]; then
      unset reset
      set --      # this resets the "$@" array so we can rebuild it
    fi
    case "$arg" in
       --help)    set -- "$@" -h ;;
       --verbose) set -- "$@" -v ;;
       --config)  set -- "$@" -c ;;
       # pass through anything else
       *)         set -- "$@" "$arg" ;;
    esac
done
# now we can process with getopt
while getopts ":hvc:" opt; do
    case $opt in
        h)  usage ;;
        v)  VERBOSE=true ;;
        c)  source $OPTARG ;;
        \?) usage ;;
        :)
        echo "option -$OPTARG requires an argument"
        usage
        ;;
    esac
done
shift $((OPTIND-1))