git pre-commit hook that automatically checks if black formatter should be applied and override files before a commit

pre-commit-black

#!/bin/bash
# Author: Kris Dorosz <cypreess@gmail.com>
# This git pre commit hook will apply black formatting before any commit and make sure all tracked files are reformatted

echo "Using" `black --version`
black --check . 2>/dev/null
if [ $? -ne 0 ]; then

    echo "Reformatting:"

    export current_git_branch=`git branch | grep \* | cut -d ' ' -f2`

    # Find all files which were reformatted by black and choose only those one which are currently tracked by git
    for f in $(comm -12 <(black . 2>&1 | grep -o '/.*\.py$' | sort) <( (git ls-tree -r --name-only  $current_git_branch; git diff --name-only --cached) | sed  "s,^,`pwd`/,g" | sort)); do
        echo "  $f"
        git add $f
    done
fi