Merge the ctest2 repository into libc

[tgross35]

libc's testing is pretty tightly coupled to ctest2, which is a reasonably simple crate that maps Rust syntax to C syntax and creates tests based off of that. ctest2 itself is a fork of ctest.

Unfortunately, relying on ctest(2) has been somewhat of a problem since it supports only a very outdated version of Rust's syntax, and there are a handful of other bugs. There have been some GSoC proposals to modernize libc and its test crates; moving ctest to a rust-lang repo makes that easier and should come with some maintenance benefits.

On Zulip, @alexcrichton confirmed ownership of the original ctest crate could be transferred to rust-lang so we can continue publishing under that name, for other repos that make use of ctest/ctest2.

This pull only brings over the repo source and history as it currently exists. I will need to follow up with integration of the CI and release workflows.

[rustbot]

@tgross35: no appropriate reviewer found, use r? to override

[tgross35]

@JohnTitor would you be okay with libc absorbing ctest2, or do you have any concerns? You can continue to maintain it here if you wish of course.

[tgross35]

Also, does anyone know of a better way to merge unrelated histories? The blame works fine but the log appears empty.

[alexcrichton]

I think I've done something like this in the past using git filter-branch which rewrites the history as-if it all happened in a subfolder which should help with log/blame by ensuring the filenames don't change abruptly

[tgross35]

r? @JohnTitor

I of course don't want to poach your fork without your okay, so I'll assign you :) if you're fine going forward, I'll get the history better integrated as Alex suggested before merging.

[JohnTitor]

Yeah, no objection. Thank you!

[JohnTitor]

Some crates use ctest2 in their tests, so maybe I should add a deprecation notice and encourage to migrate in the ctest2 once the ctest supports the modern Rust.