cp: implement `-Z`

[adysec]

GNU:

$ cp -Z
cp: Missing files to be operated on
Please try executing 'cp -- help' to obtain more information.

uutils:

$ cp -Z
error: unexpected argument '-Z' found

  tip: to pass '-Z' as a value, use '-- -Z'

Usage: cp [OPTION]... [-T] SOURCE DEST
       cp [OPTION]... SOURCE... DIRECTORY
       cp [OPTION]... -t DIRECTORY SOURCE...

For more information, try '--help'.

$ cp -- -Z
cp: missing destination file operand after "-Z"

[cakebaker]

The issue is that -Z is not implemented yet, not that you have to use --. I changed the title accordingly.

[SLASHLogin]

I think this issue can be closed with #7878

[sylvestre]

nope, a bunch of behaviors haven't been implemented
I am still working on it :)