键入：
zsh --help
给了我期望：
Usage: zsh [<options>] [<argument> ...]
Special options:
--help show this message, then exit
--version show zsh version number, then exit
-b end option processing, like --
-c take first argument as a command to execute
-o OPTION set an option by name (see below)
...
但是当我尝试时：
date --help
不做任何事情：
date: illegal option -- -
usage: date [-jnRu] [-d dst] [-r seconds] [-t west] [-v[+|-]val[ymwdHMS]] ...
[-f fmt date | [[[mm]dd]HH]MM[[cc]yy][.ss]] [+format]