git-ignore

#!/usr/bin/env bash

_parse_arguments() {
    local arg
    while (($# > 0)); do
        arg="$1"
        case "$arg" in
        --root | -R)
            _gitignore_location="${_repo_path}/.gitignore"
            ;;
        --exclude | -e)
            _gitignore_location="${_repo_path}/.git/info/exclude"
            _use_git_exclude="yes"
            ;;
        --*)
            echo "'$arg' is not a valid option"
            _invalid_option="yes"
            break
            ;;
        -*)
            echo "'$arg' is not a valid option"
            _invalid_option="yes"
            break
            ;;
        *)
            patterns+=("$arg")
            ;;
        esac
        shift
    done
    if [[ $_invalid_option == "yes" ]]; then
        return 1
    fi
    return 0
}

help_message() {
    echo "USAGE: git ignore <files> <to> <ignore>"
    exit 1
}

main() {
    ((!$#)) && help_message && exit 1
    _repo_path=$(git rev-parse --show-toplevel 2>/dev/null)
    _dotgit_folder="${_repo_path:-/non/existing}/.git"
    if [[ -z ${_repo_path} || ! -e "${_dotgit_folder}" ]]; then
        echo "fatal: not a git repository (or any of the parent directories): .git"
        return 1
    fi
    _parse_arguments "$@" || return 1
    _gitignore_location="${_gitignore_location:-${PWD}/.gitignore}"
    if [[ ! -f ${_gitignore_location} ]]; then
        touch "${_gitignore_location}"
    fi
    for pattern in ${patterns[*]}; do
        echo -n "Ignored '${pattern}'"
        [[ ${_use_git_exclude:-no} == "yes" ]] && echo -n " locally only"
        echo "${pattern}" | tee -a "${_gitignore_location}" >/dev/null
    done
}

main "$@"