Update the copyright only on changed files

update-copyright.sh

#! /usr/bin/env bash

function get_error_text {
    local readonly status="${1}"
    local message

    case "${status}" in
    1)
        message="Couldn't determine current year!"
        ;;
    2)
        message="Non-zero status from git grep command!"
        ;;
    3)
        message="Couldn't find any out of date files!"
        ;;
    4)
        message="Non-zero status when running sed!"
        ;;
    *)
        message="Unknown error"
        ;;
    esac

    echo "${message}"
    return 0
}

function error {
    >&2 echo "${@}"
}

function run_script {
    local year="$(date +"%Y")"

    if [ -z "${year}" ]; then
        error "Error: $(get_error_text 1)"
        exit 1
    fi

    # Can't get --null to work with any variety of IFS/read/for stuff. Luckily we don't have whitespace in our files
    local out_of_date_files=( $(git grep --files-with-matches --perl-regexp '@copyright \(c\) (?!'"${year}"')\d{4}' $(git diff-tree --no-commit-id --name-only -r --diff-filter=ACMTUX HEAD..master)) )
    status="${?}"

    if [ $status -ne 0 ]; then
        error "Error: $(get_error_text 2)"
        exit 2
    fi

    if [ -z "${out_of_date_files}" ]; then
        error "Error: $(get_error_text 3)"
        exit 3
    fi

    sed -i '' -e 's/@copyright (c) [[:digit:]]\{4\}/@copyright (c) '"${year}"'/g' ${out_of_date_files[@]}
    status="${?}"

    if [ $status -ne 0 ]; then
        error "Error: $(get_error_text 4)"
        exit 4
    fi

    exit 0
}

run_script "${@}"