Implement From<RawFd> for Stdio

[ariel-miculas]

Fixes #49

[polarathene]

I'm aware that there's not much point applying this feedback here given the project doesn't appear to be actively maintained. Thought I'd chime in with the feedback anyway 👍

[polarathene]

You may want to look at preferring the safe equivalents that are available now? sunfishcode/io-lifetimes#38

If a type implements AsRawFd, FromRawFd, and/or IntoRawFd, it usually wants AsFd, From<OwnedFd>, and/or From<T> for OwnedFd, respectively.

Since Rust 1.63.0 (Aug 2022), OwnedFd became available, which provides as_fd() and as_raw_fd() if you need to get BorrowedFd or RawFd types (original RFC for further context).

Suggested change

	impl From<RawFd> for Stdio {
	fn from(fd: RawFd) -> Self {
	Self {
	inner: StdioImpl::RedirectToRawFd(fd),
	}
	}
	}
	impl From<OwnedFd> for Stdio {
	fn from(fd: OwnedFd) -> Self {
	Self {
	inner: StdioImpl::RedirectToFd(fd),
	}
	}
	}

• You would also need to change the import from use std::os::unix::io::RawFd; to use std::os::fd::OwnedFd;
• There's also a AsRawFd import and a as_raw_fd() call for the RedirectToFile enum variant, that can get an OwnedFd since 1.63.0 in a similar way.

---

That said, I'm not quite sure why Stdio struct exists here instead of using the std::process::Stdio one? It already supports From for file and fd, while there is a separate function call null() for getting the equivalent /dev/null and the Keep enum variant seems to be for a No-op.

Ah.. so this is for redirection of the streams handled in the redirect_standard_streams() call further down. So at the time Rust didn't have an equivalent built-in for Stdio but it does now since Rust 1.74 (Nov 2023). So if raising the MSRV were viable, one could switch to that to simplify 😎

[ariel-miculas]

Thanks for the feedback! Unfortunately, I no longer have a use case for this feature and this PR is 2 years old, so I doubt it will be merged. Anyway, if someone decides to fork the project and find this feature useful, I'd be happy to contribute.