Add zuul pack-refs cron

Ad a cron job to pack refs in zuul repos.  Zuul creates _a lot_
of refs, packing them should make client git repo access more
efficient.  Up to a point at least -- ultimately we may still
need to delete them later.

Change-Id: Iaf5180069b38833d6e25f6880e4868d5e2319b75

modules/zuul/manifests/init.pp

@@ -222,6 +222,17 @@ class zuul (
     require    => File['/etc/init.d/zuul'],
   }
 
+  cron { 'zuul_repack':
+    user        => 'zuul',
+    weekday     => '0',
+    hour        => '4',
+    minute      => '7',
+    command     => 'find /var/lib/zuul/git/ -maxdepth 3 -type d -name ".git" -exec git --git-dir="{}" pack-refs --all \;',
+    environment => 'PATH=/usr/bin:/bin:/usr/sbin:/sbin',
+    require     => [User['zuul'],
+                    File['/var/lib/zuul/git']],
+  }
+
   apache::vhost { $vhost_name:
     port     => 443,
     docroot  => 'MEANINGLESS ARGUMENT',