Search for a configuration file in current directory upwards towards root directory the way that .gitignore and .p4config work

SearchConfigFile.rb

#!/usr/bin/env ruby

class SearchConfigFile

  def self.search (filename, directory)
    # Use current directory if directory not specified
    directory ||= Dir.getwd

    # Use expand_path to get absolute path; 1.8.7 compatible
    search_up filename, File.expand_path(directory)
  end

private
  # Search upwards for file starting from given directory
  def self.search_up (filename, directory)
    path = File.join directory, filename
    return path if File.file?(path)

    parent = File.dirname(directory)
    return if parent == directory
    search_up filename, parent
  end

end

if __FILE__ == $0
  testfile = "test.yml"
  testdir  = File.expand_path(ARGV.first || Dir.getwd)
  puts "Searching upwards for #{testfile} from #{testdir}"
  filename = SearchConfigFile.search testfile, testdir

  if filename.nil?
    puts "Not found"
    exit 1
  end

  puts filename
  exit 0
end