ZipFile.open changes file permissions when combined with Tempfile

[ZachBeta]

This is unexpected behavior and caused some trouble with file permission errors on serving files from rails through apache.

Replicated here:

# ruby-2.0.0-p247
require 'tempfile'
require 'zip/zip' # rubyzip (0.9.9)

def print_and_chmod(file)
  puts sprintf("%o", File.stat(file.path).mode)
  file.chmod(0640)
  puts sprintf("after file.chmod: %o", File.stat(file.path).mode)
  File.chmod(0640, file.path)
  puts sprintf("after File.chmod: %o", File.stat(file.path).mode)
end

File.write('foo.txt', 'foo.txt')

FileUtils.mkdir_p 'temporary_dir'
Tempfile.open('foo.zip', 'temporary_dir') do |tempfile|
  puts 'Before ZipOutputStream.open, Before ZipFile.open:'
  print_and_chmod(tempfile)

  Zip::ZipOutputStream.open(tempfile) { |zos| } # make sure it's a zip

  puts 'After ZipOutputStream.open, Before ZipFile.open:'
  print_and_chmod(tempfile)

  Zip::ZipFile.open(tempfile.path, Zip::ZipFile::CREATE) do |zip|
    zip.add(tempfile.path, 'foo.txt')
  end

  puts 'After ZipFile.open:'
  print_and_chmod(tempfile)
end

FileUtils.rm('foo.txt')

Which displays:

Before ZipOutputStream.open, Before ZipFile.open:
100600
after file.chmod: 100640
after File.chmod: 100640
After ZipOutputStream.open, Before ZipFile.open:
100640
after file.chmod: 100640
after File.chmod: 100640
After ZipFile.open:
100600
after file.chmod: 100600
after File.chmod: 100640

If you'd like me to turn this into a test for the suite, I'd be more than willing. I just need to know where to add it.