code: func LoadGlobalPatterns(fs billy.Filesystem) (ps []Pattern, err error) {
  	usr, err := user.Current()
  	if err != nil {
  		return
  	}
  
  	return loadPatterns(fs, fs.Join(usr.HomeDir, gitconfigFile))
  }
docs: // LoadGlobalPatterns loads gitignore patterns from from the gitignore file
  // declared in a user's ~/.gitconfig file.  If the ~/.gitconfig file does not
  // exist the function will return nil.  If the core.excludesfile property
  // is not declared, the function will return nil.  If the file pointed to by
  // the core.excludesfile property does not exist, the function will return nil.
  //
  // The function assumes fs is rooted at the root filesystem.