Explanation: Debian <%= scope.lookupvar('::lsbdistcodename') %>
Package: *
Pin: release o=Debian,n=<%= scope.lookupvar('::lsbdistcodename') %>
Pin-Priority: 990

Explanation: Debian <%= scope.lookupvar('::lsbdistcodename') %>-updates
Package: *
Pin: release o=Debian,n=<%= scope.lookupvar('::lsbdistcodename') %>-updates
Pin-Priority: 990

Explanation: Debian <%= scope.lookupvar('apt::next_codename') %>
Package: *
Pin: release o=Debian,n=<%= scope.lookupvar('apt::next_codename') %>
Pin-Priority: 2

Explanation: Debian sid
Package: *
Pin: release o=Debian,n=sid
Pin-Priority: 1

Explanation: Debian fallback
Package: *
Pin: release o=Debian
Pin-Priority: -10