def build_lockfile
      tree = { "SEEDS" => [] }
      self.seeds.each do |name, seed|
        if not seed.instance_of? Seeds::Seed::LocalSeed
          tree["SEEDS"] << "#{name} (#{seed.version or '$' + seed.commit})"
        end
      end
      File.write(self.lockfile_path, YAML.dump(tree))
    end
def build_lockfile
      tree = { "SEEDS" => [] }
      self.seeds.each do |name, seed|
        if not seed.instance_of? Seeds::Seed::LocalSeed
          tree["SEEDS"] << "#{name} (#{seed.version or '$' + seed.commit})"
        end
      end
      File.write(self.lockfile_path, YAML.dump(tree))
    end
Writes Seedfile.lock file.

 @!visibility private