set :git_submodules_recursive, false is broken

[bryckbost]

The way :git_submodules_recursive is retrieved, we can't get it to disable with false.

The issue is with how SCM::Base implements variable:

def variable(name, default = nil)
  if local? && configuration.exists?("local_#{name}".to_sym)
    return configuration["local_#{name}".to_sym] || default
  else
    configuration[name] || default
  end
end

Anything explicitly set to false will cause the OR conditional to return the default, which in the case of :git_submodules_recursive is nil.

We're happy to work up a patch, but want to get some feedback if there's a preferred way to approach this.

[bryckbost]

Just added a quick failing test in the collective idea fork.

[nilbus]

Fixed in #103