Function zebra_rpc::methods::height_from_signed_int

pub fn height_from_signed_int(index: i32, tip_height: Height) -> Result<Height>

Given a potentially negative index, find the corresponding Height.

This function is used to parse the integer index argument of get_block_hash. This is based on zcashd’s implementation: https://github.com/zcash/zcash/blob/c267c3ee26510a974554f227d40a89e3ceb5bb4d/src/rpc/blockchain.cpp#L589-L618