code: func LoadSystemPatterns(fs billy.Filesystem) (attributes []MatchAttribute, err error) {
  	return loadPatterns(fs, systemFile)
  }
docs: // LoadSystemPatterns loads gitattributes patterns and attributes from the
  // gitattributes file declared in a system's /etc/gitconfig file.  If the
  // /etc/gitconfig file does not exist the function will return nil. If the
  // core.attributesfile property is not declared, the function will return nil.
  // If the file pointed to by the core.attributesfile property does not exist,
  // the function will return nil. The function assumes fs is rooted at the root
  // filesystem.