Re: [PATCH v5 0/9] Introduce Rust and announce that it will become mandatory

[Patrick Steinhardt <ps@pks.im>]

On Mon, Sep 15, 2025 at 08:03:29PM -0600, Ezekiel Newren wrote:
> I am currently working on a patch series that makes Rust optional and
> addresses several concerns that this series does not:
>   * Rust calling C: Makefile has no way to build or run Rust so it
> would have to call cargo test, but that doesn't work unless build.rs
> tells cargo where libgit.a is (among other things).
>   * Build tooling alignment: My build_rust.sh is called by make and
> meson which eliminates defining how to build Rust in 2 places.
>   * Cargo vs Meson: Meson is adding support for Rust and it's getting
> better, but Cargo is the canonical build system for Rust. cargo is
> released in lockstep with rustc, and we _have_ to use cargo when
> building with make because Meson won't be available in that case.
>   * Crates: Patrick's series assumes the Git codebase is _the_ crate
>     * cbindgen: Cbindgen outputs a single header file for each crate,
> with only 1 we'll have an unmanageably large auto generated header
> file.
>     * Modularity: Using multiple crates makes Git more modular. Elijah
> told me that there was some desire to make Git more modular.
>     * Cargo Dependencies: Patrick wrote his series with Meson first in
> mind which doesn't address how we'll be able to use crates from
> crates.io
>   * CI:
>     * Sparse coverage: I think there's only one target that tests his changes.
>     * With vs Without Rust: I don't see anywhere that he covers
> building with vs without Rust in CI
>   * Build integration: Meson has to have every .rs file specified
> where as the default layout of a Rust project allows Cargo to just
> know where to look for .rs files

Yeah, as I mentioned my patch series here really aims at getting an
minimum viable user of Rust into the Git codebase so that we can focus
the discussion more on the roadmap towards Rust rather than the actual
Rust infrastructure. The whole infra is very simplistic because of that,
but that is intentional for now.

Once we have agreed on the roadmap I very much expect that we will
iterate on it to allow for more complex use cases. My next step would
have been to pick patches from your series that make all of this work
on Windows. But of course I don't have to be the (only) one to iterate
on the initial simple infrasturcture, this should ideally be an effort
by the whole community.

And yes, many of the points you mention above are things we'll have to
address over time to make Rust a viable alternative to implement
anything more complex than the trivial "varint.c" thing. I think that
iteration is key here: let's start simple and then gradually build out
the infrastructure.

Patrick