#get releases from https://github.com/wikimedia/mediawiki/releases.atom
LATEST_RELEASES=$(${WGETEXECUTABLE} -q -O- "https://github.com/wikimedia/mediawiki/releases.atom" | ${GREPEXECUTABLE} -o -P '<title>[^"]*' | ${SEDEXECUTABLE} "s/<title>//g" | ${SEDEXECUTABLE} "s/<\/title>//g")
for RELEASE in ${LATEST_RELEASES}; do
    if [[ "${RELEASE}" =~ [0-9] ]]; then
	#skip if release candidate
        if ! ${GREPEXECUTABLE} "\-rc\." <<< ${RELEASE} &>/dev/null; then
            if testvercomp ${RELEASE} "<" ${LATEST_RELEASE}; then
                LATEST_RELEASE=${RELEASE}
            fi
        fi
    fi
done

echo "latest release found: ${LATEST_RELEASE}"

#check if latest version is newer
if testvercomp ${LATEST_RELEASE} ">" ${INSTALLED_VERSION}; then
    echo "no newer version found on the interweb -> exiting"
    exit 1
fi

vercomp () {
    if [[ $1 == $2 ]]
    then
        return 0
    fi
    local IFS=.
    local i ver1=($1) ver2=($2)
    # fill empty fields in ver1 with zeros
    for ((i=${#ver1[@]}; i<${#ver2[@]}; i++))
    do
        ver1[i]=0
    done
    for ((i=0; i<${#ver1[@]}; i++))
    do
        if [[ -z ${ver2[i]} ]]
        then
            # fill empty fields in ver2 with zeros
            ver2[i]=0
        fi
        if ((10#${ver1[i]} > 10#${ver2[i]}))
        then
            return 1
        fi
        if ((10#${ver1[i]} < 10#${ver2[i]}))
        then
            return 2
        fi
    done
    return 0
}

testvercomp () {
    vercomp $1 $3
    case $? in
        0) op='=';;
        1) op='>';;
        2) op='<';;
    esac
    if [[ $op != $2 ]]
    then
        return 0
        echo 0
    else
        return 1
        echo 1
    fi
}

currently installed version: 1.35.0
test.sh: line 49: ((: 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 53: ((: 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 49: ((: 10#1 > 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 53: ((: 10#1 < 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 49: ((: 10#1 > 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 53: ((: 10#1 < 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 49: ((: 10#1 > 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 53: ((: 10#1 < 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 49: ((: 10#1 > 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 53: ((: 10#1 < 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 49: ((: 10#1 > 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 53: ((: 10#1 < 10#wmf: value too great for base (error token is "10#wmf")
latest release found: wmf-1.36.0-wmf.31-testing:
test.sh: line 49: ((: 10#wmf: value too great for base (error token is "10#wmf")
test.sh: line 53: ((: 10#wmf: value too great for base (error token is "10#wmf")