Git commit hook for python formatter black

pre-commit.sh

#!/bin/sh
# see black https://github.com/python/black

set -e

if which black >/dev/null; then
    REPO_ROOT_DIR="$(git rev-parse --show-toplevel)"

    files=$((git diff --cached --name-only --diff-filter=ACMR | grep -Ei "\.py$") || true)

    if [ ! -z "${files}" ]; then
        black $files
        git add "$files"
    fi
fi