bug#46621: Copy line

[Juri Linkov]

>> Why would one want to sacrifice a short keybinding when
>> it's easier to use a keybinding of any length to copy the
>> current line, then use C-y C-y C-y ...
>
> C-y requires moving point to bol, which is the main reason I wrote
> my own version of duplicate-line.

And I use my own version of duplicate-line that moves point
to the copied line.  This means that adding duplicate-line
to misc.el requested by this feature request was a failure.