code: func devServerBackend() backend.B {
  	pwd := os.Getenv("PWD") // os.Getwd works funny with symlinks, use PWD
  	candidates := []string{
  		filepath.Join(pwd, devCfgDir),
  		filepath.Join(filepath.Dir(pwd), devCfgDir),
  	}
  	for _, dir := range candidates {
  		if _, err := os.Stat(dir); err == nil {
  			fs, err := filesystem.New(dir)
  			if err != nil {
  				return erroring.New(err)
  			}
  			return &client.Backend{&testconfig.Provider{
  				Base: fs,
  			}}
  		}
  	}
  	return erroring.New(fmt.Errorf("luci-config: could not find local configs in any of %s", candidates))
  }
docs: // devServerConfig returns backend.B to use on a devserver.
  //
  // See New for details.