Overwrite compact on child class of Array to not return an instance of Array

This is necessary because in Ruby 1.9.3, the behavior of an internal dup of
the array (rb_ary_dup) was changed to always return an array instance, not
an instance of the actual class which it was working on.

Why can't people just stick to what works but instead try to have special
snowflakes everywhere? </rant>

lib/redmine/scm/adapters/abstract_adapter.rb

@@ -251,6 +251,14 @@ module Redmine
         def revisions
           revisions ||= Revisions.new(collect{|entry| entry.lastrev}.compact)
         end
+
+        # Required since Ruby 1.9.3 as the core compact always returns an
+        # instance of Array. This method follows the spec for Array#compact
+        def compact
+          ary = self.dup
+          ary.compact!
+          ary
+        end
       end
 
       class Info