mid-session-master-advance-rebaselisted

# Mid-Session Master Advance Rebase ## Overview When sister sessions are running in parallel and merging to the default branch, `origin/master` (or `origin/main`) advances without your worktree noticing. `git diff origin/master..HEAD` becomes misleading: it shows the **inverse** of any new upstream commits — a file added on master shows as DELETED in your diff; a line added shows as removed. Easy to mistake for cross-session contamination of your worktree. ## When to Use - Pre-push verification: `git diff origin/master..HEAD` shows unfamiliar file changes - `git status` says the working tree is clean - `git log --oneline <fork-point>..HEAD` shows only your own commits - You're in a worktree with one or more sister worktrees on other branches ## Diagnosis ```bash git fetch origin git log --oneline origin/master | head -3 # has master moved past your fork point? git log --oneline <my-branch> | head -3 # what's your branch tip? git merge-base HEAD origin/master # is your fork point now behind origin? ``` If origin/master has commits beyond your fork point, that's the source of the "spurious diff" — it is upstream's new work shown inverted, not anything in your tree. ## Fix ```bash git rebase origin/master # rebases are usually clean for non-overlapping packages — re-run the test suite to verify git diff origin/master..HEAD # now shows only your changes ``` ## Why rebase rather than just push Pushing as-is works (GitHub comput