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

2 files changed, 8 insertions, 6 deletions

diff --git a/manifests/init.pp b/manifests/init.pp
index 509b6d1..3de4d9e 100644
--- a/manifests/init.pp
+++ b/manifests/init.pp
@@ -4,6 +4,7 @@
 # See LICENSE for the full license granted to you.
 
 class apt(
+  $codename = '',
   $use_volatile = false,
   $include_src = false,
   $use_next_release = false,
@@ -38,16 +39,17 @@ class apt(
   include lsb
 
   # init $release, $next_release, $codename, $next_codename, $release_version
-  case $::lsbdistcodename {
+  case $codename {
     '': {
+      $codename = $::lsbdistcodename
       $release = $::lsbdistrelease
     }
     default: {
-      $release = debian_release($::lsbdistcodename)
+      $release = debian_release($codename)
     }
   }
-  $release_version = debian_release_version($::lsbdistcodename)
-  $next_codename = debian_nextcodename($::lsbdistcodename)
+  $release_version = debian_release_version($codename)
+  $next_codename = debian_nextcodename($codename)
   $next_release = debian_nextrelease($release)
 
   file {
diff --git a/manifests/preferences.pp b/manifests/preferences.pp
index 8f532f8..e9a74ff 100644
--- a/manifests/preferences.pp
+++ b/manifests/preferences.pp
@@ -3,8 +3,8 @@ class apt::preferences {
   concat::fragment{"apt_preferences_header":
     content => $apt::custom_preferences ? {
       '' => $::operatingsystem ? {
-        'debian' => template("apt/${::operatingsystem}/preferences_${::lsbdistcodename}.erb"),
-        'ubuntu' => template("apt/${::operatingsystem}/preferences_${::lsbdistcodename}.erb"),
+        'debian' => template("apt/${::operatingsystem}/preferences_${apt::codename}.erb"),
+        'ubuntu' => template("apt/${::operatingsystem}/preferences_${apt::codename}.erb"),
       },
       default => $custom_preferences
     },