Disable VCS Prompts on OSXFuse Volumes

## I'm using this in the agnoster theme - should work for any 
## zsh theme
## Main prompt
build_prompt() {
  RETVAL=$?
  prompt_status
  prompt_virtualenv
  prompt_context
  prompt_dir
  
  # We check if the $PWD fstype is osxfusefs - if not, 
  # load the git/mercurial prompts
  if [[ -z `df -T osxfusefs $PWD` ]]; then
      prompt_git
      prompt_hg
  fi
  prompt_end
}