Что прописать в APT::Default-Release?

3.8 How to keep a mixed system

People are sometimes interested in using one of the Debian versions as its main system distribution and one or more packages from another branch.

To set up what is your main version of Debian you should edit the /etc/apt/apt.conf (it does not usually exist, create it if you don't have one) to contain the following line:

     APT::Default-Release "version";
Where version is the version of Debian you want to use as the main distribution. The versions you can use are stable, testing and unstable. To install packages from another version, then, you must use APT in the following way:

     # apt-get -t distribution install package

$ cat /etc/apt/sources.list
deb [arch=amd64,i386] http://packages.linuxmint.com/ debian main upstream import backport romeo
deb-src http://packages.linuxmint.com/ debian main upstream import backport romeo #Added by software-properties
deb [arch=amd64,i386] http://lmde-mirror-fr-1.wedrop.it/latest testing main contrib non-free
deb [arch=amd64,i386] http://lmde-mirror-fr-1.wedrop.it/latest/security testing/updates main contrib non-free
deb [arch=amd64,i386] http://lmde-mirror-fr-1.wedrop.it/latest/multimedia testing main non-free

deb-src http://ftp.debian.org/debian/ testing main contrib non-free

deb [arch=amd64,i386] http://suwako.nomanga.net/debian sid main contrib
deb-src http://suwako.nomanga.net/debian sid main

# unstable
#deb http://mirror.yandex.ru/debian/ unstable main contrib non-free

# experimental
deb http://mirror.yandex.ru/debian/ experimental main contrib non-free