excon_multipart_form_data.rb

require 'excon'
require 'securerandom'

def multipart_form_data(buildpack_file_path)
  body      = ''
  boundary  = SecureRandom.hex(4)
  data      = File.open(buildpack_file_path)

  data.binmode if data.respond_to?(:binmode)
  data.pos = 0 if data.respond_to?(:pos=)

  body << "--#{boundary}" << Excon::CR_NL
  body << %{Content-Disposition: form-data; name="buildpack"; filename="#{File.basename(buildpack_file_path)}"} << Excon::CR_NL
  body << 'Content-Type: application/x-gtar' << Excon::CR_NL
  body << Excon::CR_NL
  body << File.read(buildpack_file_path)
  body << Excon::CR_NL
  body << "--#{boundary}--" << Excon::CR_NL

  {
    :headers => { 'Content-Type' => %{multipart/form-data; boundary="#{boundary}"} },
    :body    => body
  }
end

form_data = multipart_form_data(__FILE__)

# debug output
#puts
#form_data[:headers].each do |k,v|
  #puts "#{k}: #{v}"
#end
#puts
#puts form_data[:body]

# rough sample usage
# connection = Excon.new(...)
# connection.request(
#   :body     => form_data[:body],
#   :headers  => form_data[:headers],
#   :path     => ...,
# )