#!/bin/sh
# @(#)dpkg-dsel.sh  2009-07-01  A.J.Travis

#
# Show differences between package selections on two hosts
#

if [ $1 = '-l' ]; then
	cd /usr/local/share/dpkg-dsel
	for i in *.sel; do
		basename $i .sel
	done
	exit 0
fi
	
if [ $# -ne 2 ]; then
	echo "usage: dpkg-dsel -l # list standard package selections"
	echo "       dpkg-dsel host1 host2"
	exit 1
fi
if [ $1 = $2 ]; then
	echo "dpkg-dsel: host names must be different"
	exit 2
fi

WORK=/tmp/$$
mkdir $WORK

# extract hostname from selection file name
host1=`basename $1 .sel`
host2=`basename $2 .sel`

# reference package selection lists
ref1=/usr/local/share/dpkg-dsel/${host1}.sel
ref2=/usr/local/share/dpkg-dsel/${host2}.sel

# absolute filename
if [ -r $1 ]; then
	cmd="cat $1"

# reference selection
elif [ -r $ref1 ]; then
	cmd="cat $ref1"

# local system
elif [ $host1 = "localhost" ]; then
	cmd="dpkg --get-selections"

# remote system
else
	cmd="ssh $host1 -- dpkg --get-selections"
fi

# save selection list for first host
$cmd | grep -v 'deinstall$' | sort -o $WORK/$host1.sel

# absolute filename
if [ -r $2 ]; then
        cmd="cat $2"

# reference selection
elif [ -r $ref2 ]; then
	cmd="cat $ref2"

# local system
elif [ $host2 = "localhost" ]; then
        cmd="dpkg --get-selections"

# remote system
else
        cmd="ssh $host2 -- dpkg --get-selections"
fi

# save selection list for second host
$cmd | grep -v 'deinstall$' | sort -o $WORK/$host2.sel

# generate host1 -> host2 install list
diff $WORK/$host1.sel $WORK/$host2.sel | \
	sed -n -e '/^</s/install$/deinstall/;s/< //p' -e '/^>/s/> //p'

# tidy up
rm -r $WORK