[skarim]

Adds CLI support for base changes GitHub makes automatically when a stack's base branch is deleted. sync and rebase repair local history against the new server base without recreating the stack or its PRs.

Functionality and user impact

• Follow automatic retargets. sync and rebase use GitHub's new base and the existing validated --onto cascade to replay the stack's own commits. The local trunk changes only after rebasing succeeds; continuation keeps the accepted target, and abort restores the old trunk.
• Confirm removing unmerged base commits. If the old base is not already in the target or known to have merged into it, confirmation defaults to No. Automation can explicitly accept with --accept-base-change.
• Stop publishing against a stale base. push and submit direct users to sync before publishing a retargeted stack.
• Surface pending repair. view reports the new server base and marks the bottom branch's needsRebase in JSON without changing the saved local trunk. Remote checkout warns when an existing local stack still needs repair, and imports keep the merged first PR's old base so the next sync repairs the stack with the same consent checks.

Key areas to review

• cmd/utils.go: shared single-stack base lookup, publishing guard, and consent/cutoff selection. Only a detected retarget switches the bottom branch to --onto; ordinary trunk rebases retain their existing behavior.
• cmd/rebase.go and cmd/sync.go: target resolution, selected-range handling, and passing the cutoff into the existing rebase flow.
• cmd/rebase_worktree.go: TargetTrunk is journaled separately from the applied trunk. Check completion/save retries and abort restoration, covered by the retarget recovery cases in cmd/rebase_test.go.
• cmd/push.go, cmd/submit.go, cmd/view.go, and cmd/checkout.go: publishing guards and pending-repair reporting without implicit history rewrites. Arbitrary retargeting and branching-stack workflows remain out of scope.

[Copilot]

🔵 Needs a closer look

The history-rewriting and recovery changes have unresolved safety issues that require fixes and final human validation.

7 open issues

• Persist rebase cutoff before initial sync journal save · New
• Verify merged PR covers boundary and target ancestry · New
• Resolve cutoff against planned fast-forward tip · New
• Check ancestry independently of bottom-branch cutoff · New
• Recover fork boundary from old trunk reflog · New
• Reject stale local base when resolving rebase boundary · New
• Normalize remote-qualified trunk during comparison · New

What changed in this PR

Adds base-retarget handling to gh stack, allowing existing stacks to follow GitHub’s new base without recreating their pull requests.

Changes:

• Adds retarget detection, history repair, and --accept-base-change consent to sync and rebase.
• Records the accepted target for rebase continuation and abort recovery.
• Guards publishing against stale bases and reports pending repairs in view and checkout.

File	Description
docs/​src/​content/​docs/​reference/​cli.md	Documents retarget behavior and consent flags.
cmd/​view.go	Reports retargets and marks JSON repair status.
cmd/​view_test.go	Tests pending-repair reporting without trunk changes.
cmd/​utils.go	Adds shared detection, publishing guards, and cutoff selection.
cmd/​sync.go	Integrates retarget repair into synchronization.
cmd/​sync_test.go	Tests repair, repeat runs, and conflict rollback.
cmd/​submit.go	Blocks submission against a stale base.
cmd/​submit_test.go	Tests retarget and lookup-failure guards.
cmd/​rebase.go	Adds consent flags and target journaling.
cmd/​rebase_worktree.go	Handles target publication and original-trunk restoration.
cmd/​rebase_test.go	Tests retarget history, consent, and recovery.
cmd/​push.go	Blocks pushing against a stale base.
cmd/​push_test.go	Tests the retarget publishing guard.
cmd/​checkout.go	Uses the server base and warns about pending repairs.
cmd/​checkout_test.go	Tests tracked-stack warnings and import-base selection.

_{Review effort: Max}