bug#46621: Copy line

[Juri Linkov]

>> Maybe better to try finding a key in the 'C-x x' keymap
>> (that already contains a line-related binding 'C-x x t'
>> `toggle-truncate-lines').
>
> Unfortunately that removes some of the convenience that the command
> would bring.  I can't see anyone typing `C-x x d` (for example) 3
> times in a row to get 3 copies, much less 7 times.

But it accepts a prefix arg, so a shorter key sequence is possible:
`C-3 C-x x d`.