Bug#638024: [apt] APT::Default-Release considers equivalent suite names differently ("testing" != "wheezy")

[Filipus Klutiero <chealer@gmail.com>]

Package: apt
Version: 0.8.15.5
Severity: normal

The value of APT::Default-Release depends on what suite codenames are in 
APT sources. If a source specifies the distribution as "testing", then 
setting APT::Default-Release to "wheezy" will not work as expected. 
Instead, APT will complain that "wheezy" wasn't found in sources.list.
> E:The value 'wheezy' is invalid for APT::Default-Release as such a 
> release is not available in the sources
This requires administrators to change APT configuration, but in some 
cases APT sources too if several sources refer to the same distribution 
differently. There is also a danger in these situations that APT will 
only partially honor Default-Release. This is somewhat dangerous as one 
of the main usages of Default-Release is to maintain a testing/unstable 
mix. If the main testing source is not catched by Default-Release, the 
system will get on unstable.