bash function for switching staged packer versions

.bashrc

switch_packer () {
	TO_VER=$(echo $1 | sed "s/\./\_/g")
	HOME_BIN="$HOME/.bin"
	PACKER_BIN="$HOME/.bin/packer"
	PACKER_BIN_1_3_5="$HOME/.bin/packer-1.3.5/packer"
	PACKER_BIN_1_6_5="$HOME/.bin/packer-1.6.5/packer"
	if [ $# -eq 0 ] ; then
		echo "No packer version given, giving up."
	  	return 1
	fi

	if [ ! -d $HOME_BIN/packer-$1 ] ; then
		echo "Packer version $1 not available."
		return 1
	fi

	if [ -L $PACKER_BIN ] ; then
	 	rm $PACKER_BIN
	fi
	NEWBIN="PACKER_BIN_$TO_VER"
	ln -s ${!NEWBIN} $PACKER_BIN
}