xxx.yyy.distupgrade files in /etc/apt/sources.list - what are these?

[Colin Law]

On 6 December 2017 at 20:42, Chris Green <cl at isbd.net> wrote:
> I have just used do-release-upgrade to upgrade my system to xubuntu
> 17.10.
>
> It looks as this upgrade has created some oddly named files in
> /etc/apt/sources.list, these are:-
>
> -rw-r--r-- 1 root root  78 Dec  3 16:12 owncloud.list.distUpgrade
> -rw-r--r-- 1 root root  48 Dec  3 16:12 syncthing.list.distUpgrade
>
> Can anyone tell me what these files are for?

It seems to make copies of everything in the sources.list.d folder,
with names like that.

Colin