# File install.rb, line 52
def each_require(file, target_set, &block)
  File.foreach(file) {|line|
    next if /\A\s*require\s+['"]([^'"]+)['"]/ !~ line
    feature = $1
    filename = "#{feature}.rb"
    next if target_set.include? filename
    next if !File.exist?(filename)
    target_set[filename] = true
    yield filename
    each_require(filename, target_set, &block)
  }
end