A basic script I wrote for myself to compare package versions

diffpkg.bash

#!/bin/bash

print-usage-and-die() {
	echo "Usage: diffpkg.bash [cargo|npm] [pkg1] [pkg2]"
	echo "       pkg1 and pkg2 can have formats NAME-VERS, NAME@VERS, NAME:VERS, or NAME=VERS"
	exit 1
}

extract-name() {
	case "$1" in
		*@*)
			echo "$1" | awk -F@ '{print $1}'
			;;
		*=*)
			echo "$1" | awk -F= '{print $1}'
			;;
		*:*)
			echo "$1" | awk -F: '{print $1}'
			;;
		*-*)
			echo "$1" | awk -F- '{print $1}'
			;;
		*) print-usage-and-die ;;
	esac
}

extract-vers() {
	case "$1" in
		*@*)
			echo "$1" | awk -F@ '{print $(NF)}'
			;;
		*=*)
			echo "$1" | awk -F= '{print $(NF)}'
			;;
		*:*)
			echo "$1" | awk -F: '{print $(NF)}'
			;;
		*-*)
			echo "$1" | awk -F- '{print $(NF)}'
			;;
		*) print-usage-and-die ;;
	esac
}

case "$1" in
	cargo)
		type cargo-download 2>&1 > /dev/null || cargo install cargo-download
		name1=$(extract-name $2)
		vers1=$(extract-vers $2)
		name2=$(extract-name $3)
		vers2=$(extract-vers $3)
		set -ex
		cargo download $name1==$vers1 > $name1-$vers1.tgz
		tar -xf $name1-$vers1.tgz
		cargo download $name2==$vers2 > $name2-$vers2.tgz
		tar -xf $name2-$vers2.tgz
	;;
	npm)
		type cargo-download 2>&1 > /dev/null || cargo install cargo-download
		name1=$(extract-name $2)
		vers1=$(extract-vers $2)
		name2=$(extract-name $3)
		vers2=$(extract-vers $3)
		set -ex
		npm pack $name1@$vers1
		tar -xf $name1-$vers1.tgz
		mv package $name1-$vers1
		npm pack $name2@$vers2
		tar -xf $name2-$vers2.tgz
		mv package $name2-$vers2
	;;
	*) print-usage-and-die ;;
esac

diff -ur $name1-$vers1 $name2-$vers2