nix-diff.sh

#!/usr/bin/env bash

if [ $# -ne 2 ]; then
    echo expecting two integer arguments... aborting >&2
    exit 1
fi

profile=$(readlink ~/.nix-profile)

dirA="${profile}-$1-link"
dirB="${profile}-$2-link"

no_generation() {
    local gen="$1"
    echo no generation \`"$gen"\` found >&2
    exit 1
}

if [[ ! -L "$dirA" ]]; then
    no_generation "$dirA"
elif [[ ! -L "$dirB" ]]; then
    no_generation "$dirB"
fi

arr=tmp_files
arr_all="\${$arr[@]}"
arr_len="\${#$arr[@]}"
arr_last="\${$arr[\$(($len-1))]}"

mk_temp() {
    eval tmp=$arr_len
    tmp_files[$tmp]=$(mktemp)
}

rm_temps() {
    if [ -n "$DEBUG" ]; then
        echo DEBUG: removing temporary files >&2
    fi
    eval tmp=$arr_all
    rm -f $tmp
}

trap 'rm_temps' EXIT

mk_temp
eval versA=$arr_last
[ -n "$DEBUG" ] && echo DEBUG: "versA=$versA"

nix-store -q --references "$dirA" | sort > "$versA"

mk_temp
eval versB=$arr_last
[ -n "$DEBUG" ] && echo DEBUG: "versB=$versB"
nix-store -q --references "$dirB" | sort > "$versB"

in=$(comm -3 -1 "$versA" "$versB")
mk_temp
eval add=$arr_last
[ -n "$DEBUG" ] && echo DEBUG: "add=$add"
sed -r 's:^[^-]*-(.*)$:\1+:' <(echo "$in") \
    | grep -v env-manifest.nix \
    | sort -f \
           > "$add"

un=$(comm -3 -2 "$versA" "$versB")
mk_temp
eval rem=$arr_last
[ -n "$DEBUG" ] && echo DEBUG: "rem=$rem"
sed -r 's:^[^-]*-(.*)$:\1-:' <(echo "$un") \
    | grep -v env-manifest.nix \
    | sort -f \
           > "$rem"

cat "$rem" "$add" \
    | sort -f \
    | sed -r 's:(.*)-$:- \1:' \
    | sed -r 's:(.*)\+$:\+ \1:'

[ -n "$DEBUG" ] && sleep 2s

exit 0