On Thu, Feb 05, 2026 at 12:10:28AM +0000, brian m. carlson wrote:

On 2026-02-04 at 23:22:08, Mike Hommey wrote:

quoted

While `src/` is the default directory convention for Rust projects, it
is too generic in the context of a multi-language project that is barely
starting to (optionally) use Rust code.

Additionally, having `Cargo.toml` at the top-level of the repository
implies that one can run `cargo build` directly, but this doesn't
produce anything useful on its own.

Moving all Rust-specific files into a dedicated `rust/` subdirectory
makes things clearer.

If we're going to do this, we should place the `src` directory under the
`rust` subdirectory to maintain the normal layout.  There are many tools
that depend on this repository layout and we want to make it as easy as
possible for people to use native, standard tooling to build things.

Not that I'm going to argue your preference, but I'm curious what tools
you'd know that would not support a layout different than the typical
one, because that means they're broken with some existing crates (e.g.
those from https://github.com/servo/servo/) and should probably be
fixed.

It might also be worth moving into a rust/gitcore/src directory too,
including the crate name in the path.

Note that I don't have strong opinions for or against placing the Rust
code in a subdirectory, but I do very much want the standard layout to
be honoured.

quoted

The above is a post hoc justification. I do think it makes sense to do,
but I should mention my real immediate motivation.

git-cinnabar, a git remote helper used to talk to Mercurial servers, is
a project based on libgit (the C parts). As such, its repository
includes the git codebase as a submodule.

As of about 3 years ago, most code that is not libgit in git-cinnabar is
written in Rust, and is published on crates.io.

Part of publishing on crates.io involves running `cargo publish`, which
does `cargo package` under the hood. `cargo package` has the feature
of... not including directories that contain a Cargo.toml, so upgrading
libgit to 2.52.0 breaks the publishing process because all of the git
source code is skipped, and git-cinnabar can't be built as a result.

Of course, what this means is that this change is merely kicking the can
down the road, because the problem will reappear when the rust code
becomes non-optional in Git, thus why I'm making this RFC at the moment.

Perhaps you could ask Cargo upstream to add a feature to override that
in the meantime (or add such a feature yourself).  I can imagine other
uses for such a feature.

I'm not sure this would be well received, considering there are already
`exclude` and `include` fields to control such things, and they
explicitly and purposely don't act on directories with a Cargo.toml:

| Regardless of whether exclude or include is specified, the following
| files are always excluded:
|   - Any sub-packages will be skipped (any subdirectory that contains a
|     Cargo.toml file).
|   - A directory named target in the root of the package will be skipped.
https://doc.rust-lang.org/cargo/reference/manifest.html#the-exclude-and-include-fields

Mike