Show mode_t as octal in std::fs Debug impls Example: ```rust fn main() { println!("{:?}", std::fs::metadata("Cargo.toml").unwrap().permissions()); } ``` - Before: `Permissions(FilePermissions { mode: 33204 })` - ~~After: `Permissions(FilePermissions { mode: 0o100664 })`~~ - After: `Permissions(FilePermissions { mode: 0o100664 (-rw-rw-r--) })` ~~I thought about using the format from `ls -l` (`-rw-rw-r--`, `drwxrwxr-x`) but I am not sure how transferable the meaning of the higher bits between different unix systems, and anyway starting the value with a leading negative-sign seems objectionable.~~