UPSTREAM PR #2412: feat: add Rust closure fixtures to gix-testtools

[loci-dev]

Note

Source pull request: GitoxideLabs/gitoxide#2412

Adds ability to create fixtures using Rust closures instead of shell scripts, with manual version numbers for cache invalidation.

New API

• rust_fixture_read_only(name, version, closure) - cached read-only fixture
• rust_fixture_writable(name, version, mode, closure) - writable temp directory copy
• *_standalone variants for fixtures/ instead of tests/fixtures/

Implementation

• Version number (u32) replaces CRC-based script identity for cache invalidation
• Archives prefixed with rust- (e.g., rust-my_fixture.tar.xz)
• Reuses existing locking, archive extraction, and failure marker infrastructure

Example

let dir = gix_testtools::rust_fixture_read_only("my_fixture", 1, |dir| {
    std::fs::write(dir.join("file.txt"), "content")?;
    Ok(())
})?;

Increment version when closure behavior changes to force cache rebuild.

Original prompt

Add a way to execute Rust closures on a given directory in the gix-testtools crate, fully integrated into the existing ways of creating fixtures with scripts. The key here is to let the caller provide a version number (simple integer), that needs to be incremented manually to allow caching.
With it, it should be possible to make a fixture something like this:

let dir = gix_testtools::rust_fixture_read_only(1, |dir| { …create the fixture in Rust here })?;

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[loci-review]

The analysis encountered an error. Please review the Processing Details for more information.