Upstream Sync (microsoft/terminal → intelligent-terminal)

Cherry-pick commit-by-commit from https://github.com/microsoft/terminal into this fork, preserving per-commit attribution, auto-skipping picks that cancel each other out, and stopping cleanly the moment a human-judgment conflict appears.

You — the agent reading this file — are the orchestrator. Each step in the run is a single atomic call into one of the scripts/*.ps1 files. There is intentionally no PowerShell driver, because every interesting decision (build-fix vs. open stuck issue, retry vs. bail, finalize vs. dry-run) wants LLM judgment the operator can audit in your transcript.

When to Use This Skill

• User asks to "sync upstream", "pull from microsoft/terminal", "catch up to upstream", or "run upstream sync".
• A scheduler invokes the agent on a weekly/daily cadence.
• The previous run left an upstream-sync-stuck labeled issue open and the human has finished resolving the conflict — close the issue (that IS the lock-clear signal) and re-run.

When NOT to Use This Skill

• User wants a one-shot rebase of a single feature branch onto upstream — that's a normal git rebase, not this skill.
• An upstream-sync-stuck labeled issue is open on microsoft/intelligent-terminal — do not re-run; resolve the conflict on the stuck branch first, then close the issue.

Prerequisites

• git 2.38+ (for cherry-pick --keep-redundant-commits), gh CLI authenticated against microsoft/intelligent-terminal (needs push to upstream-sync/* topic branches + issue/label create), PowerShell 7+ (pwsh) on PATH.
• origin MUST point at microsoft/intelligent-terminal. All scripts push to origin and pass -R microsoft/intelligent-terminal explicitly. Verify with git remote -v before running.
• Full git history on origin/main (no shallow clone). Watermark discovery walks up to 5000 commits scanning for cherry picked from commit <sha> trailers. In CI, use actions/checkout@v4 with fetch-depth: 0.
• Windows build host with Visual Studio 2022, Windows SDK, vswhere, and tools\razzle.cmd / bz. Build is a hard gate before finalize.
• No state.json to bootstrap. Watermark = newest (cherry picked from commit <sha>) trailer on origin/main. If the fork has never used cherry-pick -x, run the one-time First-time sync.

State Model (no state file)

Every persistent fact lives in the source that owns it:

Why cherry-pick (not rebase or merge)

• Rebase upstream/main — ❌ fork history contains old "Merge upstream" commits; rebase replays them and explodes conflicts (verified failure on sister repo).
• Merge upstream/main — ⚠️ works, but collapses the whole sync into one blob commit, killing per-commit review and git bisect.
• Cherry-pick commit-by-commit — ✅ preserves authorship + per-commit content, allows mechanical revert-pair skipping, produces a reviewable PR.

Run a sync

Eight-step orchestration. Full commands, JSON contracts, and failure-handling for every step are in references/run-a-sync.md. The flow:

1. Preconditions (clean tree, on main FF, no open stuck issue)
2. Create branch  upstream-sync/<UTC-yyyy-MM-dd-HHmmss-rand4>
3. Fetch upstream (verify owner/repo identity of the `upstream` remote)
4. Compute pending     ← scripts/02-compute-pending.ps1  (→ JSON)
5. Cherry-pick loop    ← scripts/03-cherry-pick-one.ps1 per SHA  (→ JSON)
       picked / skipped-empty → continue
       stuck → 5a (push branch, file upstream-sync-stuck issue, EXIT)
6. (No commits picked? exit clean.)
       before build: re-pin build/pgo/Terminal.PGO.props if upstream bumped
       its Windows Terminal Major.Minor (else PGO build fails)
7. Build               ← scripts/04-try-build.ps1  (→ JSON)
       build-ok → step 8
       build-failed → ONE focused fix commit, re-build; else 7a
       build-inconclusive → 7a
   7a. Surface failure to operator, EXIT (no issue filed for build failures)
8. Finalize: push, `gh pr create`, optional `gh pr merge --rebase --auto`

Key invariants (the agent MUST hold these — full rationale in the runbook):

• Atomic per-commit. Each pick is one commit on the sync branch carrying the upstream author/date and the (cherry picked from commit <sha>) trailer. Never amend across picks.
• Stuck → exit clean. On a Tier-3 conflict (script returns status: "stuck"), do NOT continue past it — push the branch, file the labeled issue, exit. The human resolves on the stuck branch, merges (no squash), closes the issue.
• One build-fix commit, max. Build-blocking fixes land as exactly one extra commit on the sync branch. Anything bigger → exit; the operator pushes a manual fix or runs a follow-up PR.
• Never squash-merge the sync PR. Squashing destroys per-commit attribution AND the trailer the next sync uses as its watermark. The PR body banner warns reviewers; the recipe arms --rebase --auto.

Recovery procedures (rare)

Direct-to-main escape hatch, first-time watermark seeding, squash-merge recovery: references/recovery-procedures.md. Each requires explicit operator action.

After-PR review handling — fix-in-PR vs. follow-up PR

Once the sync PR is open, reviewers (Copilot + humans) will comment. Only build-blocking fixes belong on the sync branch as one focused extra commit. Everything else — code-quality, logic-bug suggestions, translation corrections, spelling-allowlist migrations, doc nits, design feedback — goes into a follow-up PR that targets the sync branch (not main). The cherry-pick PR must stay reviewable as "per-commit, faithful to upstream + minimum must-merge delta".

Full rubric, worktree mechanics, PR-body template: references/follow-up-pr.md.

Gotchas

• Never squash-merge the sync PR. Squashing destroys per-commit attribution AND collapses the trailers the next run uses as its watermark. The PR body opens with a banner; step 8 arms gh pr merge --rebase --auto.
• Never strip the (cherry picked from commit <sha>) trailer when hand-resolving a stuck pick. That trailer IS the watermark.
• Never rebase upstream/main onto this fork. Use cherry-pick — rebase replays old "Merge upstream" commits and explodes.
• Don't amend substantive review fixes into the sync PR. Only build-blocking fixes (max one extra commit). Everything else → follow-up PR.
• .github/workflows/spelling2.yml always conflicts and is always "take upstream wholesale". The Tier-0 list in references/03-known-conflicts.md handles it — extend the list when you find the next file with this pattern.
• gh pr create on Windows can fail with "Head sha can't be blank" on freshly-pushed branches. The step-8 recipe wraps it in a 3× retry. Do not "fix" it to use --head <owner>:<branch> (that points gh at a fork).
• Cherry-pick over git revert-style commits is intentional, not skipped. We only skip revert-pairs where both sides are inside the pending range. A revert of an already-merged commit must land — otherwise the fork diverges silently.
• Single-host scheduler. The stuck-lock is a read-then-check gate, not an atomic lease. Run from ONE host. For multi-host fan-out, layer atomic locking on top (GitHub Actions concurrency: upstream-sync is easiest).
• CRLF/LF on manifest files. Cherry-picks preserve upstream endings, but Tier-2 LLM-touched resolutions on .yml/.xml/.csproj/winget manifests may downgrade to LF. Re-normalize before staging — see references/03-conflict-triage.md.
• PGO pin follows upstream. build/pgo/Terminal.PGO.props hard-pins the PGO database to upstream's Windows Terminal Major.Minor (our custom.props stays 0.1, so it can't be derived). When a sync bumps the upstream version, re-pin those two values or the build fails with Could not find matching PGO package. Step 7's pre-build check covers this.

Troubleshooting

References

• references/run-a-sync.md — full eight-step procedure with commands.
• references/03-conflict-triage.md — Tier 0/1/2/3 conflict-resolution rubric.
• references/03-known-conflicts.md — files with fixed Tier-0 resolutions.
• references/follow-up-pr.md — fix-in-PR vs. follow-up PR rubric and worktree workflow.
• references/recovery-procedures.md — direct-to-main, first-time seed, squash-merge recovery.
• scripts/02-compute-pending.ps1 — derive watermark + pending list (no state file).
• scripts/03-cherry-pick-one.ps1 — cherry-pick one SHA with author/date pinning + Tier-0/Tier-1.
• scripts/04-try-build.ps1 — run bz no_clean; log to Generated Files/....