dotfiles/.local/bin/nix-user-diff

#!/bin/sh --
set -ue

: "${NIX_PROFILES_DIR:=/nix/var/nix/profiles/per-user/${USER:?}}"

generation_files() (
	cd "${NIX_PROFILES_DIR}/profile-${1:?}-link" || kill "${$}"
	fd . | sort
)

generation="${1:-$(
	nix-env --list-generations | sed -n '/current/s/\s\+\([0-9]\+\).*/\1/p'
)}"
previous_generation="${2:-$((generation - 1))}"

: "$((generation + previous_generation))"

exec 9<<EOF
$(
	{
		generation_files "${previous_generation}" 4<&- | {
			generation_files "${generation}" 3<&- | {
				diff -Naur /dev/fd/3 -
			}
		} 3<&0 <&4 4<&-

	} 4<&0
)
EOF

exec sed -n '/^[+-][^+-]/p' <&9