gulp はタスク名を補完しろよ

gulp-task-completion.zsh

compdef _gulp gulp
function _gulp () {
    local -a task
    if [ -f ./gulpfile.js ]; then
        task=(`cat gulpfile.js | grep "task('" | awk -F\' '{ print $2 }' | tr '\n' ' '`)
        compadd $task
    else
        zle -M 'No gulpfile found'
    fi
}

# https://github.com/gulpjs/gulp/blob/master/completion/zsh
# gulp --tasks-simple とかで良かった