fix(miner): check out baseBranch on the fresh-clone path so the first attempt succeeds (#9682)

[kai392]

What

ensureRepoClonedUnlocked's docstring promises both branches land on the base branch, but the fresh-clone branch returned right after git clone. A plain clone creates only origin's default-HEAD local branch, so the consumer's git worktree add -b <attempt> <path> <baseBranch> (worktree-plan.ts:80-84) can't rev-parse a bare non-default <baseBranch>. The first attempt against any repo whose base isn't the origin default fails with fatal: invalid reference: <baseBranch> (surfacing as blocked_worktree_preparation_failed), and only the second attempt — which hits the fetch+reset path that DWIM-creates the local tracking branch — works. This is reachable in production (attempt-cli.ts:578 passes the PR's real base; attempt-worktree.ts:88 defaults to "main", failing on the first attempt against any master-default repo).

How

After a successful git clone, run git checkout <baseBranch> in repoPath and return the identical { ok: false, repoPath, error: stderr || "git_checkout_failed" } shape the existing-clone branch already uses (repo-clone.ts:335-336). No fetch/reset is added — a fresh clone is already at origin's tip. The isUnsafeGitArgValue(baseBranch) guard still runs first.

Tests

Three named regression cases in test/unit/miner-repo-clone.test.ts, each failing against the current code:

1. On the first-use path with baseBranch: "develop", the injected runGit receives ["checkout", "develop"] after ["clone", ...].
2. A failing checkout on the fresh path returns { ok: false, error: "git_checkout_failed" } (and surfaces git's stderr verbatim when present).
3. The fresh path emits exactly clone then checkout — no fetch/reset.

The existing per-repo concurrency test's pinned git-op sequence is updated to include the new checkout; its non-overlapping serialization guarantee is unchanged.

Closes #9682

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Caution

🛑 LoopOver review result - fixes required

_{Review updated: 2026-07-29 20:51:06 UTC}

2 files · 1 AI reviewer · no blockers · CI failing · unstable

🛑 Suggested Action - Fix Blockers

Review summary
This fixes a real bug: `ensureRepoClonedUnlocked`'s fresh-clone branch returned immediately after `git clone` without checking out `baseBranch`, so a plain clone only has origin's default-HEAD branch locally, and the consumer's `git worktree add -b <attempt> <path> <baseBranch>` fails to rev-parse a non-default base branch on the first attempt. The fix adds a `git checkout <baseBranch>` step using the same error shape as the existing-clone path, and is well-covered by three targeted regression tests plus an updated concurrency-guard test reflecting the new op sequence. The change is narrow, correctly scoped to the described issue (#9682), and traces cleanly to the real call sites (worktree-plan.ts, attempt-cli.ts, attempt-worktree.ts) cited in the description.

Nits — 3 non-blocking

• repo-clone.ts's inline comment above the new checkout call is fairly long (4 lines) for what is a straightforward fix — could be trimmed since the docstring above `ensureRepoClonedUnlocked` already states the contract.
• The new checkout error path doesn't distinguish 'baseBranch doesn't exist on origin' from other checkout failures, but this matches the existing fetch+reset path's behavior so it's consistent, not a regression.
• Consider whether `checkoutFails`-style test coverage should also verify behavior when `baseBranch` equals the clone's default branch (checkout of an already-checked-out branch), though this is likely a no-op in git and low risk.

CI checks failing

• validate
• validate-tests

Decision drivers

• ✅ Code review — No blockers (1 reviewer)
• ✅ Gate result — Passing (No configured blocker found.)

Context & advisory signals — never blocks the verdict

Signal	Result	Evidence
Linked issue	✅ Linked	#9682
Related work	✅ No active overlap found	No same-issue or scoped active PR overlap found.
Change scope	✅ 20/20	Low review scope from cached public metadata (1 linked issue).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 89 registered-repo PR(s), 43 merged, 7 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	kai392; Gittensor profile; 89 PR(s), 7 issue(s).
Improvement	✅ Minor	risk: clean · value: minor

Linked issue satisfaction

Addressed
The diff adds the required git checkout call and identical error-shape handling right after a successful clone, guarded by the pre-existing unsafe-arg check, and includes three named regression tests covering the checkout-succeeds, checkout-fails, and no-fetch/reset-on-fresh-path cases plus an updated concurrency test asserting the new command sequence.

Review context

• Author: kai392
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: Python, Cuda, JavaScript, Kotlin, MDX, Perl, Ruby, TypeScript
• Official Gittensor activity: 89 PR(s), 7 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Keep the PR focused and include validation evidence before maintainer review.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Change scope = cached public metadata such as size labels, draft state, and review-burden hints.
• Validation posture = whether the PR provides enough public validation/test evidence for maintainer review.
• Contributor workload = public contributor activity and cleanup pressure, not a repo-wide quality failure.
• Contributor context = public GitHub/Gittensor identity context; non-Gittensor status is not a blocker.

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Decision record

• action: hold · clause: success
• config: 76c9444f465420fc9ebb0f22b459b0a68ca24b5a561dc6d694a3625cd28ddaf9 · pack: oss-anti-slop · ci: failed
• note: diverted by the randomized close-audit holdout (calibration: randomized ε-holdout on would-close PRs with propensity logging #8831) — the deterministic pipeline would otherwise have closed this PR
• record: b97e817b17366af0bb144f3c2b20a746caec63bd6e472a9b7c6e609b9bda0bcc (schema v5, head a9050f2)

_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed}

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[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

❌ 1 Tests Failed:

Tests completed	Failed	Passed	Skipped
1648	1	1647	0

View the top 1 failed test(s) by shortest run time

test/unit/miner-attempt-worktree.test.ts > prepareAttemptWorktree / cleanupAttemptWorktree (#5132) > returns ok:false with git's real stderr when git worktree add fails (e.g. an unknown base branch)

Stack Traces | 0.127s run time

AssertionError: expected undefined to be '/tmp/loopover-miner-attempt-worktree-…' // Object.is equality

- Expected:
".../cache/acme/widgets"

+ Received:
undefined

 ❯ test/unit/miner-attempt-worktree.test.ts:152:29

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