Q:

How to parse Command Line Arguments with arbitrary string

I'm trying to create a script that has an option that will contain arbitrary text (including spaces) surrounded by quotes and this is proving difficult to search for and implement. 
Basically the behavior I would like to have is docker_build_image.sh -i "image" -v 2.0 --options "--build-arg ARG=value", this will be a helper script for simplifying versioning docker images with our build server. 
The closest I've come to successfully grabbing the --options value gives me an error from getopt, "unrecognized option '--build-arg ARG=value'. 
The full script is below
#! /usr/bin/env bash
set -o errexit -o noclobber -o nounset -o pipefail
params="$(getopt -o hi:v: -l help,image:,options,output,version: --name "$0" -- "$@")"
eval set -- "$params"

show_help() {
cat << EOF
Usage: ${0##*/} [-i IMAGE] [-v VERSION] [OPTIONS...]

Builds the docker image with the Dockerfile located in the current directory. 

    -i, --image         Required.  Set the name of the image. 
    --options           Set the additional options to pass to the build command. 
    --output            (Default: stdout) Set the output file. 
    -v, --version       Required.  Tag the image with the version. 
    -h, --help          Display this help and exit. 
EOF
}

while [[ $# -gt 0 ]]
do
    case $1 in
        -h|-\?|--help)
            show_help
            exit 0
            ;;
        -i|--image)
            if [ -n "$2" ]; then
                IMAGE=$2
                shift
            else
                echo -e "ERROR: '$1' requires an argument.\n" >&2
                exit 1
            fi
            ;;        
        -v|--version)            
            if [ -n "$2" ]; then
                VERSION=$2
                shift
            else
                echo -e "ERROR: '$1' requires an argument.\n" >&2
                exit 1
            fi
            ;;
        --options)
        echo -e "OPTIONS=$2\n"
            OPTIONS=$2
        ;;
        --output)            
            if [ -n "$2" ]; then
                BUILD_OUTPUT=$2
                shift
            else
                BUILD_OUTPUT=/dev/stderr
            fi
        ;;
        --)
            shift
            break
        ;;
        *)
            echo -e "Error: $0 invalid option '$1'\nTry '$0 --help' for more information.\n" >&2
            exit 1
        ;;
    esac
shift
done

echo "IMAGE: $IMAGE"
echo "VERSION: $VERSION"
echo ""

# Grab the SHA-1 from the docker build output
ID=$(docker build ${OPTIONS} -t ${IMAGE}  .  | tee $BUILD_OUTPUT | tail -1 | sed 's/.*Successfully built \(.*\)$/\1/')

# Tag our image
docker tag ${ID} ${IMAGE}:${VERSION}
docker tag ${ID} ${IMAGE}:latest

A:

Just handle it like you handle the others that take an argument (image and version).  i.e. add the colon marking a mandatory argument to the option string that goes to getopt, and pick the value off of $2.  
I think the error you get comes from getopt, since it's not told that options takes an argument, and so it tries to interpret --build-arg ARG=value as a long option (it does start with a double-dash). 
$ cat opt.sh
#! /bin/bash
params="$(getopt -o hv: -l help,options:,version: --name "$0" -- "$@")"
eval set -- "$params"

while [[ $# -gt 0 ]] ; do
    case $1 in
        -h|-\?|--help)
            echo "help"
            ;;
        -v|--version)            
            if [ -n "$2" ]; then
                echo "version: <$2>"
                shift
            fi
            ;;
        --options)            
            if [ -n "$2" ]; then
                echo "options: <$2>"
                shift
            fi
            ;;
    esac
    shift
done

$ bash opt.sh --version 123 --options blah --options "foo bar"
version: <123>
options: <blah>
options: <foo bar>

