Simplify setting multiple environment variables using templates

envtemplater

#!/bin/bash

ENVTEMPLATER_SEPARATOR='%'

if [[ -z "$1"  || $1 = "--help" ]]; then
    echo >&2 "Usage: T_template1=substitution1 ... T_templateN=substitutionN envtemplater arg%...%template ... arg%...%template -- command [arguments]"
    echo >&2 "Example: T_github=ALTURL_%0%=https://github.com/vi/%0% envtemplater dive%github fdlinecombine%github -- submodule_update_alturl.sh --force"
    exit 1
fi

while [ "$1" != '--' ]; do
    if [[ $# == 0 ]]; then
        echo >&2 "-- not found in command line"
        exit 4;
    fi

    IFS="$ENVTEMPLATER_SEPARATOR"
    Q=($1)
    IFS='
'
    #for i in ${Q[@]}; do
    #    echo "$i"
    #done
    TEMPLATE=T_${Q[${#Q[@]}-1]}
    TEMPLATE_CONTENT=$(eval "echo \"\$$TEMPLATE\"")
    if [ -z "$TEMPLATE_CONTENT" ]; then
        echo >&2 "Template $TEMPLATE not found"
        exit 2
    fi
    IFS="$ENVTEMPLATER_SEPARATOR"
    TEMPLATE_ARRAY=($TEMPLATE_CONTENT)
    IFS='
'
    VALUE=""
    MODE=val
    for i in "${TEMPLATE_ARRAY[@]}"; do
        if [[ $MODE == val ]]; then
            VALUE="${VALUE}$i"
            MODE=arg
        else
            if [[ $i -lt 0 || $i -gt ${#Q[@]}-1 ]] || ! [ $i -eq $i ]; then
                echo >&2 "$i is out of bounds or not a number for $TEMPLATE_CONTENT in $1"
                exit 3
            fi
            VALUE="${VALUE}${Q[$i]}"
            MODE=val
        fi
    done
    eval "export $VALUE"
    shift
done
shift

exec "$@"

Please update your script from here:
https://gist.github.com/2bfb3ea296648f12049c1c8b3350baea.git