060e033df9
Before the flag was stabilized, it required two arguments of the form "from=<from_path>" and "to=<to_path>" respectively. The stabilized version uses one argument of the form "<from_path>=<to_path>". Unfortunately the old format is still parsed successfully, but results in attempting to replace the literal paths "from" and "to". https://github.com/rust-lang/rust/issues/41555#issuecomment-320951103