code: func findSiteRoot(p string) string {
  	for {
  		if isSiteRoot(p) {
  			return p
  		}
  		// Dir returns "/" (or C:\\) when it encounters the root directory. It is
  		// the only case when Dir(...) return value ends with separator.
  		parent := filepath.Dir(p)
  		if parent[len(parent)-1] == filepath.Separator {
  			// It is possible disk root has .cipd directory, check it.
  			if isSiteRoot(parent) {
  				return parent
  			}
  			return ""
  		}
  		p = parent
  	}
  }
docs: ////////////////////////////////////////////////////////////////////////////////
  // Site root path resolution.
  // findSiteRoot returns a directory R such as R/.cipd exists and p is inside
  // R or p is R. Returns empty string if no such directory.