I originally installed Debian stretch, which at the time was "stable". I needed some newer packages that it didn't have, so I upgraded to Debian testing, which was buster. Currently my `lsb_release -a` command returns Debian 10 (buster).

It seems that recently Debian changed its packages so now I get a message from Synaptic:

```
Repository 'http://deb.debian.org/debian stretch Release' changed its 'Suite' value from 'stable' to 'oldstable'
This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details.
Repository 'http://ftp.us.debian.org/debian testing InRelease' changed its 'Codename' value from 'buster' to 'bullseye'

```

Ok, makes sense. However, I don't want to upgrade to bullseye yet. I want to stay on buster, and when I decide to upgrade to bullseye, I'll do so manually. How should I edit my repos to accomplish this? Currently my repos look like this:

```
$ grep ^ /etc/apt/sources.list /etc/apt/sources.list.d/*
/etc/apt/sources.list:# deb cdrom:[Official Debian GNU/Linux Live 9.9.0 cinnamon 2019-04-27T11:50]/ stretch main 
/etc/apt/sources.list:# deb cdrom:[Official Debian GNU/Linux Live 9.9.0 cinnamon 2019-04-27T11:50]/ stretch main 
/etc/apt/sources.list:
/etc/apt/sources.list:deb http://ftp.us.debian.org/debian/ testing main non-free contrib 
/etc/apt/sources.list:deb-src http://ftp.us.debian.org/debian/ testing main non-free contrib 
/etc/apt/sources.list.d/base.list:deb http://deb.debian.org/debian/ stretch main 
/etc/apt/sources.list.d/base.list:# deb-src http://deb.debian.org/debian/ stretch main 
/etc/apt/sources.list.d/base.list:
/etc/apt/sources.list.d/base.list:
/etc/apt/sources.list.d/base.list:
/etc/apt/sources.list.d/base.list:
/etc/apt/sources.list.d/base.list:
/etc/apt/sources.list.d/base.list:
/etc/apt/sources.list.d/home:hawkeye116477:waterfox.list:deb http://download.opensuse.org/repositories/home:/hawkeye116477:/waterfox/Debian_9.0/ /
/etc/apt/sources.list.d/home:manuelschneid3r.list:deb http://download.opensuse.org/repositories/home:/manuelschneid3r/Debian_9.0/ /
/etc/apt/sources.list.d/nodesource.list:deb https://deb.nodesource.com/node_12.x stretch main
/etc/apt/sources.list.d/nodesource.list:deb-src https://deb.nodesource.com/node_12.x stretch main

```