configure 248 Bytes
if [ "$#" -eq 1 ]; then
    # use specific version
    old=$1
else
    # use last release
    old=$(git rev-list --tags --max-count=1)
fi
mkdir -p tmp
cp ../../dist/echarts.js "tmp/newEcharts.js"
git show $old:dist/echarts.js > 'tmp/oldEcharts.js'