Msgpack commands

[devyn]

Description

I thought about bringing nu_plugin_msgpack in, but that is MPL with a clause that prevents other licenses, so rather than adapt that code I decided to take a crack at just doing it straight from rmp to Value without any rmpv in the middle. It seems like it's probably faster, though I can't say for sure how much with the plugin overhead.

@IanManske I started on a Read implementation for RawStream but just specialized to from msgpack here, but I'm thinking after release maybe we can polish it up and make it a real one. It works!

User-Facing Changes

New commands:

• from msgpack
• from msgpackz
• to msgpack
• to msgpackz

Tests + Formatting

Pretty thorough tests added for the format deserialization, with a roundtrip for serialization. Some example tests too for both from msgpack and to msgpack.

• 🟢 toolkit fmt
• 🟢 toolkit clippy
• 🟢 toolkit test
• 🟢 toolkit test stdlib

After Submitting

• update release notes

[devyn]

I did a few last minute things here:

• from msgpack --objects, like from json --objects, with no delimiter. Just keeps reading any valid msgpack data in a stream. I thought this could be handy for inspecting dumps of the plugin protocol since that's basically what it does
• without --objects, checks to ensure we actually reached EOF. this is important in case the data is corrupt or we don't handle it properly, because we don't want to return success in that case.
• moved the tests to nu-command, where they should be

There is something kind of unusual I've done where I'm generating the fixtures with a nu script. In order to prevent anything obfuscated from sneaking in, I'm running that script for each test, but this does obviously depend on nu working correctly, which maybe isn't the best thing for a test to depend on.

However, I tried writing the alternative in Rust with all of the comments and it was just horrible, very hard to follow. Nu's binary syntax makes it a lot better.

I could just check in those MessagePack fixtures already generated as binary instead, I just worry that if someone goes to update it and then the script returns something different than before in some other random fixture, it's going to be very confusing.

[fdncred]

let's go! thanks!