Add to ~/.vagrant.d directory to put vagrant meta directories (hence VM) in a common directory based on the current directory name.

Vagrantfile

# -*- mode: ruby -*-
# vi: set ft=ruby :

if !ARGV.find { |arg| /global/ =~ arg } and !ENV['VAGRANT_DOTFILE_PATH'] and File.exists?('.vagrant.keep')
  if !ENV['VAGRANT_COMMON_DIRECTORY_ROOT']
    abort '.vagrant.keep file is present but VAGRANT_COMMON_DIRECTORY_ROOT is not set'
  end

  pn = Pathname::pwd
  ENV['VAGRANT_DOTFILE_PATH'] = "#{ENV['VAGRANT_COMMON_DIRECTORY_ROOT']}/#{pn.basename}"

  puts 'metadata directory: ' + ENV['VAGRANT_DOTFILE_PATH']
  if File.directory?('.vagrant')
    #puts 'removing .vagrant directory'
    FileUtils.rm_r('.vagrant') if File.directory?('.vagrant')
  end
  system 'vagrant ' + ARGV.join(' ')
  abort
end