命令行参数前的「-」和「--」有什么区别？
https://www.zhihu.com/question/267095526
http://commons.apache.org/proper/commons-cli/index.html
git中有的命令参数为什么使用一个横杠 - 有的命令却使用两个横杠 -- ?
https://www.zhihu.com/question/41366215
shell命令行中flag的使用方法
https://blog.csdn.net/c359719435/article/details/78785156
Command-Line Options
http://www.catb.org/esr/writings/taoup/html/ch10s04.html
What's the difference between a flag, an option, and an argument?
https://unix.stackexchange.com/questions/285575/whats-the-difference-between-a-flag-an-option-and-an-argument
