fix(server): a pull that fast-forwards no longer fails on large Git output

[ScottN-PV]

Problem

pullCurrentBranch runs git pull --ff-only under the default 1 MB output cap with truncation off, so output past the cap fails the command. A large fast-forward prints a diffstat over 1 MB. The pull applies, and the Pull action and automatic pull still report it as failed (#17358).

Change

The pull now drains and bounds its output with appendTruncationMarker: true, as the commit-context and range reads already do. After a successful pull, HEAD before and after decides the result, so the text is not needed. A pull Git rejects still fails with Git's exit code.

Scope and approval

Closes #17358. The triage comment confirms the cause on main and proposes this change. PR #14702 edits the same call for a different reason; whichever lands second needs a one-line rebase.

Verification

An agent ran these checks. No person tested the change.

• Real pull on Linux over the reporter's range: a clone at 2188bdd8b5 tracking a local mirror of d81afa0a6f (13,764 files). git pull --ff-only prints 1,549,556 bytes. On main the driver fails with "Git output exceeded 1000000 bytes" after HEAD has already moved to d81afa0a6f. With this change it returns pulled, and a second pull returns skipped_up_to_date.
• New tests in GitVcsDriverCore.test.ts pull a real clone whose git pull stdout or stderr is padded past 1 MB: both report pulled with HEAD at the remote tip. A diverged branch still fails with exit code 128, not an output-cap error. All three fail on main.
• apps/server: vp test run src/vcs, 7 files, 264 tests pass. Typecheck passes. vp lint and vp fmt --check on the two changed files pass, with two lint warnings main already has.
• Not run through the Pull button in a client. The real pull above calls the driver method the Pull action and automatic pull use.

Model: Claude Opus 5.5, Claude Fable 5.1 (review), GPT-6-Astra (review). Harness: Claude Code, Codex.

[macroscopeapp]

Approvability

Verdict: Approved at 51fd066

Macroscope's review found this PR approvable — This is a small, well-contained server bug fix: large git pull output is truncated instead of incorrectly failing an already-applied fast-forward, while genuine pull failures remain errors. Tests cover both output streams and the rejected-pull case.

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[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between b0ee7dd and 51fd066.

📒 Files selected for processing (2)

• apps/server/src/vcs/GitVcsDriverCore.test.ts
• apps/server/src/vcs/GitVcsDriverCore.ts

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📝 Walkthrough

Walkthrough

pullCurrentBranch now truncates oversized Git pull output instead of failing because the output exceeds the cap. Tests cover successful fast-forwards and rejected pulls with oversized output.

Changes

Git pull output handling

Layer / File(s)	Summary
Truncate pull output and verify results apps/server/src/vcs/GitVcsDriverCore.ts, apps/server/src/vcs/GitVcsDriverCore.test.ts	pullCurrentBranch enables output truncation. Tests verify oversized stdout and stderr do not prevent successful fast-forwards, and that a rejected pull still reports its exit code.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Low

Suggested reviewers: juliusmarminge

Merge Risk: ⚪ Minimal · up to 51fd0

Large Git pull output should no longer cause an otherwise successful pull to fail. No actionable merge-blocking risk remains after normal checks.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check		The title clearly and concisely describes the main change: successful fast-forward pulls no longer fail when Git output exceeds the cap.
Description check		The description includes the required Problem, Change, Scope and approval, and Verification sections. It explains the issue, implementation, linked issue and approval context, focused test coverage, o…
Linked Issues check		Issue #17358 requires successful fast-forward pulls to remain successful when Git output exceeds 1,000,000 bytes, while keeping output bounded and preserving Git exit handling. pullCurrentBranch now…
Out of Scope Changes check		The source change is limited to the pull output handling. The added tests cover the large-output success case and the non-fast-forward failure case required by issue #17358. No unrelated change is est…

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