pbuilder git tree: Changes to 'exp'

[Mattia Rizzolo]

New branch 'exp' available with the following commits:
commit 9ae2cf64331ca9cbaab1dec0217fc034f69abde3
Author: Mattia Rizzolo <mattia at debian.org>
Date:   Sat Mar 19 15:11:14 2016 +0000

    modules: stop overriding APT::Default-Release for experimental
    
    This override has been in place since the first support for experimental.
    Though 'APT::Default-Release = "experimental"' is always a really really bad
    idea, as it causes all packages to be upgraded to the the experimental version,
    and always building using packages from experimental also when not needed.
    
    Nowdays dependency resolvers are clever enough to understand when they need to
    pick a package from experimental and when not to better satisfy the build-deps.
    
    This makes pbuilder behaves more similar to Debian buildd's, and makes its
    behaviour more inline with all the other partial overlay suites (e.g. like
    *-backports).
    
    This also means that starting from now packages needing packages from
    experimental will need to mark the Build-Depedency with a version constriction
    (but this is most likely a non-issue, given that this is already need for
    packages uploading to the Debian archive).