strip_leading_dir is not always reliable with tar archives

[zimbatm]

I don't know why yet exactly why but the prefix folder in the following archive is not stripped correctly.

If I run the tar xzvf --strip-components=0 or --strip-components=1 I still get the "moodle" sub-folder. --strip-components=2 does strip it though.

If I try to run tar -tzvf you can see that all files are prefixed with "./" which might be the reasons of the difference.

ark "moodle" do
  url "http://downloads.sourceforge.net/project/moodle/Moodle/stable24/moodle-latest-24.tgz?r=&ts=1362482456&use_mirror=heanet"
  version '2.4.1'
  action :install
end