postinst is in lxqt-openssh-askpass 0.12.0-3.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27  | #!/bin/sh
# postinst script for #PACKAGE#
#
# see: dh_installdeb(1)
set -e
case "$1" in
    configure)
        update-alternatives --install /usr/bin/ssh-askpass ssh-askpass /usr/bin/lxqt-openssh-askpass 15 \
            --slave /usr/share/man/man1/ssh-askpass.1.gz ssh-askpass.1.gz /usr/share/man/man1/lxqt-openssh-askpass.1.gz
        # invalid alternatives are automatically reconfigured
        ls -L /etc/alternatives/ssh-askpass >/dev/null 2>&1 || update-alternatives --auto ssh-askpass
    ;;
    abort-upgrade|abort-remove|abort-deconfigure)
    ;;
    *)
        echo "postinst called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac
exit 0
 |