refactor new function name, use hardhat- namespace
correct/expd docstring, hardhat-safe-file-truename
save 1 repeated function call
OK to treat nil FILENAME same as file-truename
does in hardhat-safe-file-truename per discussion with @DarwinAwardWinner, PR #9
make unsafe remote file-truename customizable
doc bugs/workarounds re: remote file-truename