fix for $lsbdistcodename regression introduced by ac166366d7baa45b74e09974289d9fb2dad38e67

What happened here was the $codename = $::lsbdistcodename was removed from
init.pp and replaced with just $::lsbdistcodename whereever $codename was
used. Then in the sources.list.erb and preferences files things were changed
like this:

<pre>+### Debian current: <%= codename = scope.lookupvar('::lsbdistcodename') %>
...
-deb <%= debian_url %> <%= codename %> <%= repos %>
...
+deb <%= debian_url=scope.lookupvar('apt::debian_url') %> <%= codename %> <%= repos=scope.lookupvar('apt::repos') %>
</pre>

This meant that the codename was always set to lsbdistcodename, and you because
in newer puppet versions you cannot assign a value to a top-level facter
variable, it is not possible to change this.

Because we cannot change $lsbdistcodename, we have to fix this by allowing the
user to pass a different, non-top-level scoped variable to the class as a
parameter, which defaults to $::lsbdistcodename, so that upgrades can be
triggered.

This is documented in the README in an upgrade notice

4 files changed, 14 insertions, 14 deletions

diff --git a/templates/Debian/preferences_lenny.erb b/templates/Debian/preferences_lenny.erb
index 4648ce1..5c3c829 100644
--- a/templates/Debian/preferences_lenny.erb
+++ b/templates/Debian/preferences_lenny.erb
@@ -1,4 +1,4 @@
-Explanation: Debian <%= scope.lookupvar('::lsbdistcodename') %>
+Explanation: Debian <%= codename=scope.lookupvar('apt::codename') %>
 Package: *
 Pin: release o=Debian,a=<%= scope.lookupvar('apt::release') %>,v=<%= scope.lookupvar('apt::release_version') %>*
 Pin-Priority: 990
@@ -8,9 +8,9 @@ Package: *
 Pin: origin backports.debian.org
 Pin-Priority: 200
 
-Explanation: Debian <%= scope.lookupvar('apt::next_release') %>
+Explanation: Debian <%= next_release=scope.lookupvar('apt::next_release') %>
 Package: *
-Pin: release o=Debian,a=<%= scope.lookupvar('apt::next_release') %>
+Pin: release o=Debian,a=<%= next_release %>
 Pin-Priority: 2
 
 Explanation: Debian sid
diff --git a/templates/Debian/preferences_squeeze.erb b/templates/Debian/preferences_squeeze.erb
index e74515e..efe7720 100644
--- a/templates/Debian/preferences_squeeze.erb
+++ b/templates/Debian/preferences_squeeze.erb
@@ -1,16 +1,16 @@
-Explanation: Debian <%= scope.lookupvar('::lsbdistcodename') %>
+Explanation: Debian <%= codename=scope.lookupvar('apt::codename') %>
 Package: *
-Pin: release o=Debian,n=<%= scope.lookupvar('::lsbdistcodename') %>
+Pin: release o=Debian,n=<%= codename %>
 Pin-Priority: 990
 
-Explanation: Debian <%= scope.lookupvar('::lsbdistcodename') %>-updates
+Explanation: Debian <%= codename %>-updates
 Package: *
-Pin: release o=Debian,n=<%= scope.lookupvar('::lsbdistcodename') %>-updates
+Pin: release o=Debian,n=<%= codename %>-updates
 Pin-Priority: 990
 
-Explanation: Debian <%= scope.lookupvar('apt::next_codename') %>
+Explanation: Debian <%= next_codename=scope.lookupvar('apt::next_codename') %>
 Package: *
-Pin: release o=Debian,n=<%= scope.lookupvar('apt::next_codename') %>
+Pin: release o=Debian,n=<%= next_codename %>
 Pin-Priority: 2
 
 Explanation: Debian sid
diff --git a/templates/Debian/preferences_wheezy.erb b/templates/Debian/preferences_wheezy.erb
index e8c15d6..0cc0e5c 100644
--- a/templates/Debian/preferences_wheezy.erb
+++ b/templates/Debian/preferences_wheezy.erb
@@ -1,11 +1,11 @@
-Explanation: Debian <%= scope.lookupvar('::lsbdistcodename') %>
+Explanation: Debian <%= codename=scope.lookupvar('apt::codename') %>
 Package: *
-Pin: release o=Debian,n=<%= scope.lookupvar('::lsbdistcodename') %>
+Pin: release o=Debian,n=<%= codename %>
 Pin-Priority: 990
 
-Explanation: Debian <%= scope.lookupvar('::lsbdistcodename') %>-updates
+Explanation: Debian <%= codename %>-updates
 Package: *
-Pin: release o=Debian,n=<%= scope.lookupvar('::lsbdistcodename') %>-updates
+Pin: release o=Debian,n=<%= codename %>-updates
 Pin-Priority: 990
 
 Explanation: Debian sid
diff --git a/templates/Debian/sources.list.erb b/templates/Debian/sources.list.erb
index ddfcaab..04c13ea 100644
--- a/templates/Debian/sources.list.erb
+++ b/templates/Debian/sources.list.erb
@@ -1,7 +1,7 @@
 # This file is managed by puppet
 # all local modifications will be overwritten
 
-### Debian current: <%= codename = scope.lookupvar('::lsbdistcodename') %>
+### Debian current: <%= codename=scope.lookupvar('apt::codename') %>
 
 # basic
 deb <%= debian_url=scope.lookupvar('apt::debian_url') %> <%= codename %> <%= lrepos=scope.lookupvar('apt::real_repos') %>