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

[Chris Green]

On Thu, Dec 07, 2017 at 01:57:47PM +0000, Colin Law wrote:
> 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.
> 
Yes, but why?  I *guess* it might be so it's simple to restore the
non-Ubuntu PPAs by just copying the files back but it would be nice to
know and have it documented somewhere.

-- 
Chris Green