// LoadIndexWithDecoder loads the index and decodes it with fn.
func LoadIndexWithDecoder(repo restic.Repository, id restic.ID, fn func(io.Reader) (*Index, error)) (idx *Index, err error) {
debug.Log("Loading index %v", id.Str())
buf, err := repo.LoadAndDecrypt(restic.IndexFile, id)
if err != nil {
return nil, err
}
idx, err = fn(bytes.NewReader(buf))
if err != nil {
debug.Log("error while decoding index %v: %v", id, err)
return nil, err
}
idx.id = id
return idx, nil
}