I've pushed a branch wip-rav1e to Savannah:

https://git.savannah.gnu.org/cgit/guix.git/log/?h=wip-rav1e

With this branch I can successfully (slowly!) encode AV1 video using
librav1e in FFmpeg.

I need some advice about the Rust packages. I used Martin Becze's
recursive version-aware Rust crate importer [0] to create the packages,
with some manual changes to the rav1e package.

Should they be added to (gnu packages crates-io)? And if so, should it
be done as a single commit? Or one-by-one? It's 258 new packages, and
figuring out the order they should be added in seems... too hard. So I'd
rather do it all at once.

The c-bindgen and cargo-c packages could go in (gnu packages rust-apps).

What about updating them later? Will `guix refresh` handle it? Or will I
need to re-import? In that case, would it be easier to keep them all in
their own module?

[0] https://issues.guix.info/issue/38408