find_gems_with_sources

# File lib/rubygems/dependency_installer.rb, line 85
  def find_gems_with_sources(dep)
    # Reset the errors
    @errors = nil
    gems_and_sources = []

    if @domain == :both or @domain == :local then
      Dir[File.join(Dir.pwd, "#{dep.name}-[0-9]*.gem")].each do |gem_file|
        spec = Gem::Format.from_file_by_path(gem_file).spec
        gems_and_sources << [spec, gem_file] if spec.name == dep.name
      end
    end

    if @domain == :both or @domain == :remote then
      begin
        # REFACTOR: all = dep.requirement.needs_all?
        requirements = dep.requirement.requirements.map do |req, ver|
          req
        end

        all = !dep.prerelease? &&
              # we only need latest if there's one requirement and it is
              # guaranteed to match the newest specs
              (requirements.length > 1 or
                (requirements.first != ">=" and requirements.first != ">"))

        found, @errors = Gem::SpecFetcher.fetcher.fetch_with_errors dep, all, true, dep.prerelease?

        gems_and_sources.push(*found)

      rescue Gem::RemoteFetcher::FetchError => e
        if Gem.configuration.really_verbose then
          say "Error fetching remote data:\t\t#{e.message}"
          say "Falling back to local-only install"
        end
        @domain = :local
      end
    end

    gems_and_sources.sort_by do |gem, source|
      [gem, source =~ /^http:\/\// ? 0 : 1] # local gems win
    end
  end