dpkg/debian/dpkg.preinst

#!/bin/sh -e
# This script can be called in the following ways:
#
# Before the package is installed:
#	<new-preinst> install
#
# Before removed package is upgraded:
#	<new-preinst> install <old-version>
#
# Before the package is upgraded:
#	<new-preinst> upgrade <old-version>
#
#
# If postrm fails during upgrade or fails on failed upgrade:
#	<old-preinst> abort-upgrade <new-version>

# Handle upgrades from pre-conffile dpkg.cfg
upgrade_dpkg_non_conffile()
{
    if [ -r /etc/dpkg/dpkg.cfg ]; then
	dpkg_cfg_md5="535552ad5ee9145dbc7a34c264df4e59  /etc/dpkg/dpkg.cfg"
	if echo "$dpkg_cfg_md5" | md5sum -c >/dev/null 2>&1; then
	    echo "Removing non-modified dpkg.cfg to be replaced by a conffile ..."
	    rm -f /etc/dpkg/dpkg.cfg
	fi
    fi
}

clean_alternative()
{
    ALTDIR="/var/lib/dpkg/alternatives"
    if [ -e "$ALTDIR/$2" ]; then
        if [ -e "$ALTDIR/$1" ] && grep -q "^$2$" "$ALTDIR/$1"; then
            echo "Removing conflicting alternative $2 ..."
            rm -f "$ALTDIR/$2"
        fi
    fi
}

case "$1" in
    install)
	;;

    upgrade)
        # Cleanup bad alternatives that would choke with new
        # update-alternatives (see #530633, #531611)
        clean_alternative x-terminal-emulator x-terminal-emulator.1.gz
        clean_alternative x-session-manager x-session-manager.1.gz

	case "$2" in
	    # Upgrade from pre-conffile dpkg.cfg
	    1.9.21 | 1.10.* )
		upgrade_dpkg_non_conffile
		;;
	esac
	;;

    abort-upgrade)
	;;


    *)
	echo "$0 called with unknown argument \`$1'" 1>&2
	exit 1
	;;
esac

#DEBHELPER#
exit 0