pre-commit hook to run `black` for python auto-formatting

pre-commit

#!/bin/sh

# make sure black is available
which black > /dev/null 2>&1
if [ $? -ne 0 ]; then
    echo "Unable to run precommit hook, black is not available"
    exit 1
fi

# find any staged py files
files="$(git diff --name-only --cached | grep '.*\.py$' | paste -sd ' ' -)"
if [ "$files" == "" ]; then
    echo "No files to reformat, skipping"
    exit 0
fi

# run the autoformatting, your settings from pyproject.toml will be picked up.
black $files

# re-stage
git add $files