support snappy format

[figsoda]

closes #202

Also removed remaining mentions of incorrect lz extensions that wasn't removed in #198

[marcospb19]

Nice, does the Snappy format has any MIME bytes to be add to the tests?

[figsoda]

yes, application/x-snappy-framed, but infer doesn't support it
file-format supports it but is not nearly as popular, maybe we can try that
didn't check but magic (libmagic binding) might support it as welll

[marcospb19]

For reference, we have some MIME checks implemented here:

ouch/src/utils/fs.rs

Lines 65 to 121 in bafc2d3

	pub fn try_infer_extension(path: &Path) -> Option<Extension> {
	fn is_zip(buf: &[u8]) -> bool {
	buf.len() >= 3
	&& buf[..=1] == [0x50, 0x4B]
	&& (buf[2..=3] == [0x3, 0x4] || buf[2..=3] == [0x5, 0x6] || buf[2..=3] == [0x7, 0x8])
	}
	fn is_tar(buf: &[u8]) -> bool {
	buf.len() > 261 && buf[257..=261] == [0x75, 0x73, 0x74, 0x61, 0x72]
	}
	fn is_gz(buf: &[u8]) -> bool {
	buf.starts_with(&[0x1F, 0x8B, 0x8])
	}
	fn is_bz2(buf: &[u8]) -> bool {
	buf.starts_with(&[0x42, 0x5A, 0x68])
	}
	fn is_xz(buf: &[u8]) -> bool {
	buf.starts_with(&[0xFD, 0x37, 0x7A, 0x58, 0x5A, 0x00])
	}
	fn is_lz4(buf: &[u8]) -> bool {
	buf.starts_with(&[0x04, 0x22, 0x4D, 0x18])
	}
	fn is_zst(buf: &[u8]) -> bool {
	buf.starts_with(&[0x28, 0xB5, 0x2F, 0xFD])
	}
	let buf = {
	let mut buf = [0; 270];
	// Error cause will be ignored, so use std::fs instead of fs_err
	let result = std::fs::File::open(&path).map(|mut file| file.read(&mut buf));
	// In case of file open or read failure, could not infer a extension
	if result.is_err() {
	return None;
	}
	buf
	};
	use crate::extension::CompressionFormat::*;
	if is_zip(&buf) {
	Some(Extension::new(&[Zip], "zip"))
	} else if is_tar(&buf) {
	Some(Extension::new(&[Tar], "tar"))
	} else if is_gz(&buf) {
	Some(Extension::new(&[Gzip], "gz"))
	} else if is_bz2(&buf) {
	Some(Extension::new(&[Bzip], "bz2"))
	} else if is_xz(&buf) {
	Some(Extension::new(&[Lzma], "xz"))
	} else if is_lz4(&buf) {
	Some(Extension::new(&[Lz4], "lz4"))
	} else if is_zst(&buf) {
	Some(Extension::new(&[Zstd], "zst"))
	} else {
	None
	}
	}

So, this could probably be reused in our tests?

If you wish to, I can merge this as it is, and then you can create an issue for covering the rest of it.

Or, you can try to solve everything in this PR.

[figsoda]

I thought about reusing it by checking the warnings generated by the program, but #220 (just opened btw) might cause tests to fail

I don't plan on addressing this in this pull request