pre-commit-template

#!/usr/bin/env bash

DEBUG=0

debug_echo() {
    if [ "$DEBUG" -ne "0" ]; then
        echo "$*"
    fi
}

trap cleanup EXIT SIGHUP SIGINT SIGTERM

temp_files=()

cleanup() {
    # cleanup after yourself!
    debug_echo "deleting ${temp_files[@]}"
    rm -f "${temp_files[@]}"
}

executable=$1

# tweaked the answer from
# https://stackoverflow.com/a/49265008/1175053
for file in `git diff --name-only --cached --diff-filter=d | grep '\.py$'`; do
    debug_echo "$executable: processing $file"
    if `git diff --quiet "$file"`; then
        # no dirty version in working tree,
        # modify the file directly and git-add
        $executable --quiet "$file"
        git add "$file"
    else
        # need to leave working tree untouched, so 
        # save staged contents of file to temp file
        # and process that
        temp_and_orig_files=(`git checkout-index --temp "$file"`)
        temp_file=${temp_and_orig_files[0]}
        temp_files+=("$temp_file")
        $executable --quiet "$temp_file"
        # manually create the blob from modified temp
        # file and update the original file in the index
        hash=`git hash-object -w "$temp_file"`
        git update-index --add --cacheinfo 100644 "$hash" "$file"
    fi
done

# If no files left in index after formatting - fail
if `git diff --staged --quiet`; then
    1>&2 echo "$executable: No files to commit after reformatting"
    exit 1
fi