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

[Eli Zaretskii]

> From: Juri Linkov <juri@linkov.net>
> Cc: zkanfer@gmail.com,  64185@debbugs.gnu.org,  me@eshelyaron.com
> Date: Thu, 22 Jun 2023 20:27:04 +0300
> 
> > Patches welcome, but if you want to have this in Emacs 29, please
> > hurry up with the patches.
> 
> This is both simple and general allowing to specify any number
> for the new line position counting from the first/last line,
> but only values 0, 1, and -1 are really useful:

Thanks, this LGTM, with one comment:

> +(defcustom duplicate-line-pos 0
> +  "Where to put point after copying the line.

A better name for this would be duplicate-line-final-position or maybe
duplicate-line-point-position.

Also, please mention this variable in NEWS, where duplicate-line is
announced.