Method append

src/butil/iobuf.cpp:1029–1034

void IOBuf::append(const IOBuf& other) {
    const size_t nref = other._ref_num();
    for (size_t i = 0; i < nref; ++i) {
        _push_back_ref(other._ref_at(i));
    }
}

void IOBuf::append(const Movable& movable_other) {
    if (empty()) {