#!/bin/bash

FROM="$1"
OLD_FILE="$(mktemp)"
NEW_FILE="$(mktemp)"

declare -A old
git show "$FROM:go.mod" \
    | sed -n -e '6 { /require/ b x; :x { p; n; /)/ q; b x} }' > "$OLD_FILE"
while IFS= read -r line; do
  x=( $line )
  old[${x[0]}]=${x[1]}
done < "$OLD_FILE"

declare -A new
cat go.mod \
    | sed -n -e '6 { /require/ b x; :x { p; n; /)/ q; b x} }' > "$NEW_FILE"
while IFS= read -r line; do
  x=( $line )
  new[${x[0]}]=${x[1]}
done < "$NEW_FILE"

for index in ${!new[@]}; do
    if [[ -n $old[$index] ]] && [[ ${old[$index]} != ${new[$index]} ]]; then
        echo "- \`$index\` from ${old[$index]} to ${new[$index]}"
    fi
done