post_install() {
  grep -qe '^/usr/bin/elvish$' etc/shells || echo '/usr/bin/elvish' >> etc/shells
  grep -qe '^/bin/elvish$' etc/shells || echo '/bin/elvish' >> etc/shells
}

pre_remove() {
  sed -ri -e '\|^/usr/bin/elvish$|d' -e '\|^/bin/elvish$|d' etc/shells
}