The following series of commits are made to get Nix machinery working.

The majority of the work on the patch was reworking some testing machinery by adding generator for commits so that we can easily populate a repository for testing purposes – avoiding using the native repository which wouldn’t work (easily) with nix flake check.

nix: remove nix tooling in favour of future flake.nix

Removing the Nix tooling managed by niv in favour of a future flake.nix.

fmt: remove .rustfmt.toml

The formatting configuration is not worth the maintenance of a nightly version. Remove it and allow the default formatting to be used instead.

test: improve commit and submodule testing

Two of the tests in radicle-git-ext and radicle-surf relied on using the Git repository itself. This can end up being an issue when sandboxing is involved.

This improves the situation by being able to generate commit data to add to a temporary repository.

It also adds a helper for creating a local, temporary submodule for testing the submodule interactions in the radicle-surf API.

nix: add Nix flake

Add the Nix flake machinery for developing using Nix tooling.

This requires that the following are added:

• Cargo.lock
• rust-toolchain

To ensure that versions are pinned.