Script for merging two Git repositories

migrate.sh

#!/bin/bash

set -e

base_commit=30b923863d1768121c1ffb95932977e4283eceea
config_tree=56ecfa52fa08335c44ebcc9a8749779b3b9a7ecc

make_tree() {
    sway_config=$1

    new_config="$( (
        set -e
        git ls-tree $config_tree &&
        echo "040000 tree $sway_config	sway"
    ) | git mktree)"

    (
        set -e
        echo "040000 tree $new_config	configs"
        git ls-tree $base_commit | grep -v $config_tree
    ) | git mktree
}

current_commit="$(git rev-parse HEAD)"

result_commit="$(git rev-list --reverse sway/main | (while IFS=$'\n' read -r sway_commit; do
    sway_tree="$(git rev-parse "$sway_commit^{tree}")"
    merged_tree=$(make_tree "$sway_tree")
    message="Sway: $(git show --format=%B --no-patch "$sway_commit")"
    merged_commit="$(git commit-tree -p "$current_commit" -m "$message" "$merged_tree")"

    current_commit=$merged_commit
done

echo "$current_commit")
)"

echo "$result_commit"