Remove hard coded edition fallback #531
Description
This hard coded edition is becoming a problem:
Line 75 in 889b9a7
There are multiple issues related to this open already but for very specific symptoms. I think the best early move would be to just remove the hard coded fallback entirely. The rustfmt program itself has it's own fallback mechanism, and people can use the options to pass a default if they want.
The issue now is that rustfmt refuses to accept the argument being specified twice and any attempt to use the currently available settings to use the users preferred fallback results in an error.
The idea of also parsing Cargo.toml has been floated in comments on other issues, but I would suggest it would be better to let users specify their rustfmt_command as cargo fmt -- instead which would accomplish that. Again this solution is currently blocked because it gets overridden by hard coded argument!