def fill_changelogs
      [].tap do |threads|
        gemfile.changes.each do |gem_name, details|
          threads << Thread.new { retrieve_gem_changes(gem_name, details) }
        end
      end.each(&:join)
    end
def fill_changelogs
      [].tap do |threads|
        gemfile.changes.each do |gem_name, details|
          threads << Thread.new { retrieve_gem_changes(gem_name, details) }
        end
      end.each(&:join)
    end
For each gem, retrieve its changelog