#
# fun with rubygems new mechanism to generate the actual
# name for the gem command with different real and imaginary
# ruby vms
#
save_ruby_name = Gem::ConfigMap[:RUBY_INSTALL_NAME]
%w{ruby jruby rubinius rbx ruby1.9 ironruby duby rubydubydoo rubyruby}.collect do |ruby_name| 
  Gem::ConfigMap[:RUBY_INSTALL_NAME]=ruby_name
  Gem.default_exec_format % "gem"
end

# => ["gem", "jgem", "rubinius", "rbx", "gem1.9", "irongem", "duby", "gemdubydoo", "gemruby"]
#
# and if you want to restore your original Gem::ConfigMap[:RUBY_INSTALL_NAME]
#
Gem::ConfigMap[:RUBY_INSTALL_NAME] = save_ruby_name

# Deduce Ruby's --program-prefix and --program-suffix from its install name.
def self.default_exec_format
  baseruby = ConfigMap[:BASERUBY] || 'ruby'
  ConfigMap[:RUBY_INSTALL_NAME].sub(baseruby, '%s') rescue '%s'
end