old_contents: #!/usr/bin/env python
  
  import os
  import os.path
  import shutil
  
  pwd = os.path.dirname(os.path.realpath(__file__))
  
  def install_config_file(config_file_name, symlink_name):
      full_symlink_name = os.path.expanduser(symlink_name)
  
      if os.path.exists(full_symlink_name):
          shutil.move(full_symlink_name, full_symlink_name + ".old")
      else:
          dirname = os.path.dirname(full_symlink_name)
          if not os.path.exists(dirname):
              os.makedirs(dirname)
  
      os.symlink(pwd + "/" + config_file_name, full_symlink_name)
  
  install_config_file("zshrc", "~/.zshrc")
  install_config_file("emacs.el", "~/.emacs.d/init.el")
  install_config_file("vimrc", "~/.vimrc")
  install_config_file("Xmodmap", "~/.Xmodmap")
  install_config_file("vimperatorrc", "~/.vimperatorrc")
  
new_contents: #!/usr/bin/env python
  
  import os
  import os.path
  import shutil
  
  pwd = os.path.dirname(os.path.realpath(__file__))
  
  def install_config_file(config_file_name, symlink_name):
      full_symlink_name = os.path.expanduser(symlink_name)
  
      if os.path.exists(full_symlink_name):
          shutil.move(full_symlink_name, full_symlink_name + ".old")
      else:
          dirname = os.path.dirname(full_symlink_name)
          if not os.path.exists(dirname):
              os.makedirs(dirname)
  
      os.symlink(pwd + "/" + config_file_name, full_symlink_name)
  
  install_config_file("zshrc", "~/.zshrc")
  install_config_file("emacs.el", "~/.emacs.d/init.el")
  install_config_file("vimrc", "~/.vimrc")
  install_config_file("Xmodmap", "~/.Xmodmap")
  install_config_file("tmux", "~/.tmux.conf")
  
subject: Add tmux file to installation script