Git pre-commit hook to check copyright headers for current year

pre-commit.sh

#!/bin/sh

readonly FILES=$(git diff --diff-filter=ACMRTUXB --cached --name-only)
readonly CURRENT_YEAR=$(date +"%Y")

for f in $FILES; do
    head -10 $f | grep -i copyright 2>&1 1>/dev/null || continue

    if ! grep -i -e "copyright.*$CURRENT_YEAR" $f 2>&1 1>/dev/null; then
        INVALID_FILES="$INVALID_FILES $f"
    fi
done

if [ -n "$INVALID_FILES" ]; then
    echo "The following files have an invalid copyright year specified:"
    for f in $INVALID_FILES; do
        echo "    $f"
    done
    exit 1
fi