Fix rebase treating queued PRs as merged

[skarim]

• Fixes gh stack rebase: queued PR treated as merged, causing incorrect rebases for downstream branches #144

gh stack rebase (and gh stack sync, which shares the same cascade-rebase code) treated a queued PR as if it had already merged. When a branch's PR was in the merge queue, the rebase skipped that branch and then rebased the branches above it --onto trunk, dropping the queued branch's commits from every downstream branch:

✓ Skipping aerendel/mixed-content-types1 (PR #9333 queued)
✓ Rebased aerendel/mixed-content-types2 onto main (adjusted for merged PR)
✓ Rebased aerendel/mixed-content-types3 onto aerendel/mixed-content-types2 (adjusted for merged PR)

A queued PR is not merged into trunk yet — its commits only exist on its own branch, which is frozen while it sits in the merge queue. Rebasing the branches above it onto trunk therefore discarded work that those downstream branches depend on.

Root cause

cascadeRebase (cmd/utils.go) branched on BranchRef.IsSkipped(), which is IsMerged() || IsQueued(). Both merged and queued branches set needsOnto = true, activating the git rebase --onto path that drops the skipped branch's commits from downstream branches. That is correct for a merged PR — its commits really are in trunk — but wrong for a queued PR. The --onto seed in runRebase (cmd/rebase.go) shared the same conflation for --upstack.

Behavior

Merged and queued branches are now handled differently during a cascade rebase:

• Merged branch — unchanged: its commits are in trunk, so downstream branches rebase --onto the first non-merged ancestor to drop them.
• Queued branch — the branch itself is still skipped (it is frozen in the merge queue and is not rebased or pushed), but downstream branches now rebase normally onto the queued branch, keeping its commits underneath. They are no longer moved onto trunk.
• A queued branch sitting between a merged branch and an active branch keeps the active branch stacked on it; the merged branch's commits cannot be dropped while the frozen queued branch still carries them.

gh stack sync gets the same fix, since it calls the shared cascadeRebase helper.

Changes

cmd/utils.go:

• cascadeRebase splits the skip handling — a merged branch sets needsOnto / ontoOldBase as before, while a queued branch resets needsOnto so downstream branches rebase onto it instead of trunk. The --onto target search now skips only merged ancestors (queued ancestors keep their commits, so they are valid targets).

cmd/rebase.go:

• runRebase only seeds --onto mode when the branch immediately below the range IsMerged() (was IsSkipped()), so a queued predecessor no longer forces the first in-range branch onto trunk.
• continueRebase resolves its display base against IsMerged() for consistency.

Testing

cmd/rebase_test.go — a queuedPRClient helper (drives the transient queued state through syncStackPRs via a merge-queue entry) plus:

• TestRebase_QueuedBranch_DownstreamStaysStacked: downstream branches rebase onto the queued branch, not --onto trunk, with no "adjusted for merged PR".
• TestRebase_MergedBelowQueued_KeepsStackedOnQueued: a branch above a queued branch stays stacked on it even when a merged branch sits below.
• TestRebase_UpstackAboveQueuedBranch: --upstack above a queued branch rebases onto the queued predecessor.

cmd/sync_test.go:

• TestSync_QueuedBranch_DownstreamStaysStacked: the same behavior through sync, and the queued branch is excluded from the push.

go vet ./... is clean and the full go test -race -count=1 ./... suite passes.

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[Copilot]

Pull request overview

Fixes queued PR handling during cascade rebases so downstream branches retain queued commits.

Changes:

• Distinguishes merged and queued branches in rebase logic.
• Corrects --upstack and continuation base selection.
• Adds rebase and sync regression tests.

Show a summary per file

File	Description
cmd/utils.go	Preserves queued branches as downstream rebase bases.
cmd/rebase.go	Updates --onto selection logic.
cmd/rebase_test.go	Adds queued-branch rebase coverage.
cmd/sync_test.go	Adds queued-branch sync coverage.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 1
• Review effort level: Medium