spec_prep updates git repos if target exists

I am frequently without internet access and have configured rake to not clear my fixtures directory upon success with:

task :spec => []; Rake::Task[:spec].clear
task :spec do
  Rake::Task[:spec_prep].invoke
  Rake::Task[:spec_standalone].invoke
end

This updates fixture modules if they're already present, otherwise works as before.  My other thought would be to add a new task (spec_update?) that just accomplished this.