After advanceIntegrationBranchRef ff-updates refs/heads/<integrationBranch>,
the merger now enumerates other worktrees on that branch and reconciles
each one's index + working tree to the new tip via syncWorktreeToHead.
Not a git pull — origin may still be at the previous tip without
pushAfterMerge, so pull --ff-only is a no-op and a naive stash/pull/pop
ends with the worktree restored to the old state. Instead the new
worktree-ref-sync helper:
1. Diffs the worktree against the previous tip to isolate real edits
from the stale-index "phantom diff" against the new HEAD.
2. Snaps clean worktrees forward via reset --hard HEAD.
3. In stash-and-ff mode with real edits, captures them as a binary patch
against the previous tip, snaps to HEAD, then git apply --3way to
restore. Untracked files are saved + restored separately. Patch
conflicts surface as synced-with-pop-conflict with the patch left on
disk for manual recovery.
Per-worktree outcome emitted as merge:auto-sync (new GitMutationType).
Per-step pull:fast-forward / stash:push / stash:pop / stash:pop-conflict
that pass through the auditor are tagged metadata.autoSync=true.
Isolated in its own try-catch so an auto-sync failure can't fail the
already-landed merge. Default behavior is mergeAdvanceAutoSync="stash-and-ff";
"off" preserves the legacy surprise behavior.
Backstopped by merger-auto-sync.slow.test.ts: clean-sync snaps both index
and files forward, ff-only with real edits is a no-op, stash-and-ff
preserves untracked locals across the snap, task worktrees on fusion/fn-*
are skipped, empty branch map emits nothing.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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