string_view read_until(string_view&, sep)

[OlafvdSpek]

inline std::string_view read_until(std::string_view& v, char sep)
{
	size_t i = v.find(sep);
	std::string_view ret = v.substr(0, i);
	v.remove_prefix(i == std::string_view::npos ? i : i + 1);
	return ret;
}

I find it quite useful, perhaps it could be added to the library.