test: separate reftable semantics from production latency budgets

[teamleaderleo]

Reftable semantic tests inherit the production two-second Git-read budget while running real subprocesses alongside the rest of the package. The full package reproduces a failure in metadataUsesGitResolvedWorktreeBranchAndWatchesReftableStorage even though the suite passes in isolation. Temporary local instrumentation showed a successful rev-parse starting with 14 ms remaining and taking 33 ms; the reader correctly rejected it as incomplete after the deadline.

Give these real-process semantic tests an explicit 15-second budget through existing injection points. For the ambient-repository test, use the executable that successfully created the reftable fixture, so environment isolation is tested independently of backend fallback. Preserve branch, commit, watch-path, unborn-branch, and fallback assertions, and add a direct check that an expired reference read remains unreadable without starting Git. Production code and its deadlines are unchanged.

Validation: baseline full-package runs failed locally; the test-first commit also fails the existing linked-worktree test (208 tests, 1 issue). With the fix, the full package passes, including the deadline/process-termination tests. A separate full run with Git 2.53 preferred for fixture creation also passes 208 tests. Builds use two compiler jobs locally, without launching the app. No hosted diagnostic run was dispatched.

This is a scoped reliability fix, not a claim that the original CI failure is conclusively explained: #13163 failed plumbingIgnoresAmbientRepositorySelection, which still passes in isolation locally, and CI's Homebrew Git is 2.55 rather than the local versions. Hosted confirmation remains pending.

Related: #13095, #13163.

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Summary by cubic

Reftable semantic tests were inheriting the production two-second Git-read budget, so real-process assertions could time out when the full package runs in parallel. They now use an explicit 15-second wall-time budget; production code and deadlines are unchanged.

Changes

• Adds a direct assertion that an expired reference read returns .unreadable without starting Git.
• Uses the executable that created the reftable fixture for the ambient-repository test so environment isolation is tested independently of backend fallback.
• Preserves the existing branch, commit, watch-path, unborn-branch, and fallback assertions.

Validation

• Full package passes locally (208 tests) with default Git and with Git 2.53 preferred for fixture creation.
• Related: [RFC] CI structure: thin router, reusable platform workflows, merge queue, failure ratchet #13095, test: stop the XCTest import warning flood #13163; test: stop the XCTest import warning flood #13163 remains unexplained by this scoped fix and hosted confirmation is pending.

^{Written for commit 23b61fe. Summary will update on new commits.}

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Reviewing files that changed from the base of the PR and between 1cd76eb and 23b61fe.

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• Packages/macOS/CmuxGit/Tests/CmuxGitTests/ReftableGitMetadataTests.swift

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[github-actions]

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[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge because it only adjusts test configuration and adds focused deadline coverage without changing production behavior.

Summary

This PR separates reftable semantic test execution from the production Git-read latency budget without changing production behavior.

• Gives real-process reftable tests an explicit 15-second bound.
• Pins the ambient-repository isolation test to the Git executable that created its fixture.
• Adds coverage proving an already-expired reference deadline returns unreadable metadata without launching Git.

_{Reviews (1) · Last reviewed commit: "test: isolate reftable semantics from pr..."}

[teamleaderleo]

Duplicate of #13186, which merged. Both fixed the same reftable test flake in the same file.