[01/08] add gitoxide boundary and typed OID alias storage dependencies

[mjc]

Why this PR exists:

• This PR introduces the dependency and module boundary foundations used by the rest of the gitoxide migration stack.
• It adds gix plus related worktree crates so later PRs can read Git data through gitoxide instead of continuing to spread libgit2-shaped reads through the app.
• It adds iddqd as the future typed-ID storage dependency for commit/OID aliasing.
• It also adds the small support dependencies needed by the upcoming graph/alias work: rustc-hash and smallvec.
• It keeps interactive behavior unchanged; the only app-facing addition is the benchmark-only --exit-when-graph-complete flag used to measure the stack consistently.

What changed in this PR:

• Adds the gitoxide dependency set:
  • gix
  • gix-worktree
  • gix-worktree-state
• Adds future compact identity-storage dependencies:
  • iddqd
  • rustc-hash
  • smallvec
• Adds src/git/gix.rs as the initial gitoxide boundary module.
• Exposes git::gix from src/lib.rs.
• Exposes git::test_support under #[cfg(test)] and moves shared test fixture helpers behind that boundary so later PRs can reuse them without expanding production behavior.
• Adds small compatibility helpers touched by the setup work, including branch-name visibility/localisation test support.
• Adds the benchmark-only --exit-when-graph-complete CLI path and graph-completion wait helper.
• Updates Cargo.lock for the new dependency graph.

What the new git::gix boundary currently contains:

• A shared history object-cache size constant.
• A helper to enable the history object cache on a gix::Repository.
• Commit-graph access helpers and a commit-count hint.
• A branch-tip iterator for local and remote branches.
• A small adapter for converting gitoxide errors into the existing git2::Error shape.

What iddqd is for, in a follow-on PR:

The graph pipeline needs to refer to the same commits from multiple layers: walker, batcher, buffer, renderer, heatmap, app state, and query integration.

Passing raw Git object IDs everywhere would keep cloning, hashing, comparing, and converting object IDs across those layers. It would also leak the libgit2/gitoxide boundary into too many call sites.

The intended follow-up is to store each commit object ID once and pass a small typed alias through the rest of the app. iddqd is added here so that storage choice can be reviewed separately from the later behavior migration.

Algorithm difference:

• Adds dependency and helper wiring only.
• Adds the initial gitoxide boundary module.
• Adds shared test-support wiring used by later stack layers.
• Adds a benchmark-only headless completion path so every branch can be timed the same way.
• Does not change interactive graph walking.
• Does not change query behavior.
• Does not change rendering behavior.
• Does not change mutating Git actions.
• Does not yet introduce the actual commit alias map.

Performance story:

• Enabling branch only; no direct interactive runtime win is claimed here.
• The headless completion flag exists so the whole stack can be measured consistently without opening the TUI.

Benchmark Results for the whole stack

Command shape: hyperfine --warmup 5 './target/release/guitar /home/mjc/src/linux --exit-when-graph-complete'.

CPU: M1 MacBook Pro 16GB

Ref	Total	vs main	User	System	CPU
main	2:37.28	1.00x	118.00s	7.88s	80%
01-gix-boundary	1:43.99	1.51x	97.85s	2.33s	96%
02-gix-oids	1:14.26	2.12x	65.41s	2.17s	91%
03-graph-walker	5.816s	27.05x	1.82s	0.74s	43%
04-queries-readonly	3.812s	41.26x	1.47s	0.42s	49%
05-actions-network	1.993s	78.91x	1.47s	0.26s	87%
06-app-integration	1.826s	86.13x	1.51s	0.10s	88%
06-app-integration	1.879s	83.70x	1.44s	0.11s	82%
07-draw-status	1.618s	97.21x	1.36s	0.08s	89%

CPU: 5950x Linux/ZFS

Ref	Total	vs main	User	System	CPU
main	1:39.24	1.00x	96.16s	1.72s	98%
01-gix-boundary	1:46.41	0.93x	101.28s	3.82s	98%
02-gix-oids	1:10.85	1.40x	69.07s	1.78s	100%
03-graph-walker	2.094s	47.39x	1.59s	0.55s	102%
04-queries-readonly	1.856s	53.47x	1.58s	0.46s	110%
05-actions-network	1.862s	53.30x	1.60s	0.49s	112%
06-app-integration	1.639s	60.55x	1.40s	0.22s	98%
07-draw-status	1.632s	60.81x	1.34s	0.18s	93%
08-bench-docs	1.629s	60.92x	1.36s	0.19s	94%

Memory: 5950x Linux/ZFS

Ref	Peak heap	Peak RSS
main	1.26G	2.81G
01-gix-boundary	1.26G	2.82G
02-gix-oids	1.38G	2.63G
03-graph-walker	455.13M	1.15G
04-queries-readonly	436.12M	977.18M
05-actions-network	436.12M	978.61M
06-app-integration	419.89M	853.30M
07-draw-status	419.89M	916.59M
08-bench-docs	419.89M	988.71M

[Copilot]

Pull request overview

This PR lays the groundwork for a staged migration toward gitoxide by introducing a dedicated git::gix boundary module and adding the dependency set needed for upcoming graph/alias work. It also centralizes common Git test fixtures under git::test_support and adds a benchmark-only headless mode (--exit-when-graph-complete) to consistently measure graph completion.

Changes:

• Add gitoxide-related dependencies (gix, gix-worktree, gix-worktree-state) plus future typed-ID storage deps (iddqd, rustc-hash, smallvec).
• Introduce src/git/gix.rs as the initial gitoxide boundary and expose it via src/lib.rs.
• Add benchmark-only graph-completion waiting/shutdown helpers and refactor tests to use shared git::test_support helpers (including a language guard).

Reviewed changes

Copilot reviewed 21 out of 22 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/tests/helpers/localisation.rs	Uses shared language guard and switches temp language file creation to tempfile.
src/tests/helpers/keymap.rs	Uses shared language guard to avoid cross-test localisation leakage.
src/tests/git/queries/remotes.rs	Uses shared init_repo_at test helper for consistent repo setup.
src/tests/git/queries/diffs.rs	Uses shared init_repo_at in temp repo helper; renames local seeded init helper.
src/tests/git/actions/reverting.rs	Uses shared init_repo_at test helper for consistent repo setup.
src/tests/git/actions/rebasing.rs	Uses shared init_repo_at test helper for consistent repo setup.
src/tests/git/actions/merging.rs	Uses shared init_repo_at test helper for consistent repo setup.
src/tests/git/actions/cherrypicking.rs	Uses shared init_repo_at test helper for consistent repo setup.
src/tests/git/actions/branching.rs	Uses shared init_repo_at test helper for consistent repo setup.
src/tests/core/graph_service.rs	Uses shared init_repo_at test helper for consistent repo setup.
src/tests/app/state/app.rs	Adds tests for wait_until_graph_complete behavior.
src/tests/app/input/navigation.rs	Uses shared init_repo_at and language guard in settings-language test.
src/tests/app/input/git.rs	Uses shared init_repo_at test helper for consistent repo setup.
src/tests/app/draw/settings.rs	Uses shared language guard for localisation-dependent rendering assertions.
src/main.rs	Adds --exit-when-graph-complete mode and argument-to-repo-path parsing.
src/lib.rs	Exposes git::gix and (test-only) git::test_support.
src/helpers/branch_visibility.rs	Adds byte-slice refname parsing helper for gitoxide reference names.
src/git/test_support.rs	Introduces reusable test fixtures for repos, worktrees, commits, and localisation guard.
src/git/gix.rs	Adds initial gitoxide boundary utilities (commit-graph hint, branch tip iteration, error adapter).
src/app/app.rs	Adds bootstrap helper, graph completion waiting, and background graph shutdown logic; improves disconnect handling in sync().
Cargo.toml	Adds new dependencies for gitoxide and upcoming typed-ID/graph work.
Cargo.lock	Updates lockfile for the new dependency graph.

Comments suppressed due to low confidence (1)

src/tests/git/queries/diffs.rs:66

• init_seeded_repo_at uses Repository::init, which can pick the initial branch name from the developer/CI Git config (e.g. init.defaultBranch). That makes these tests less deterministic than the new shared test_support::init_repo_at, which pins the initial HEAD.

To keep submodule fixtures consistent across environments, reuse crate::git::test_support::init_repo_at here instead of Repository::init + manual user config.

fn init_seeded_repo_at(path: &Path) -> Repository {
    fs::create_dir_all(path).unwrap();
    let repo = Repository::init(path).unwrap();
    {
        let mut config = repo.config().unwrap();

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[mjc]

I did say I'd get around to this, so here we are!

There is still a bunch of libgit2 left to remove/narrow around diffs etc but I did the hardest bits in this 8-stack.

Sorry about how massive it is, but that was really unavoidable.

I will happily help get it all ship-shape and mergeable.

the test linux kernel repo I used is 2.3 million commits, 44 remotes.

libgit2's worktree support is the one relevant area where gitoxide/gix are not full-featured enough. So dumping it entirely will take quite a lot more work.

Happy to answer any questions or help in any way.

The CLI flag I added isn't required but it made profiling and heaptracking startup much easier...

[mjc]

also - the later PRs look huge because they contain all the previous PRs in the stacks' changes. as these get merged they should get easier to review.