bug#64185: proposal for new function: copy-line

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Cc: Zachary Kanfer <zkanfer@gmail.com>,  64185@debbugs.gnu.org,
>   me@eshelyaron.com
> Date: Thu, 22 Jun 2023 09:57:31 +0300
> 
> > We could have the prefix arg of - (i.e., "C-u - M-x ...") produce that
> > behavior from duplicate-line.
> 
> The problem is how to define this behavior with the prefix arg C-u in case
> when a prefix numeric argument is used.
> 
> > Or we could have a user option to do that regardless of the argument,
> > but then we should decide on which of the N new lines to put point:
> > the first one copied or the last one.
> 
> A user option looks preferable.  In case of a prefix numeric argument,
> it also makes sense to have 3 choices:
> 
> 1. leave point on the old line
> 2. move point to the first new line
> 3. move point to the last new line

Patches welcome, but if you want to have this in Emacs 29, please
hurry up with the patches.