Drill — Detached-HEAD Rescue

# Drill — Detached-HEAD Rescue ## The brief On-call engineer checks out a release tag to reproduce a stakeholder's number, makes a "quick fix" commit while detached, then `git switch main` — the fix vanishes from all branches the night before a reporting deadline. ## Starter state (seed script) ```bash mkdir rescue-drill && cd rescue-drill git init && git switch -c main for i in 1 2 3 4 5; do echo "v$i" >> report.py; git add . && git commit -m "report v$i"; done git tag v1.2 git checkout v1.2 # DETACHED HEAD echo "fix off-by-one in totals" >> report.py git add . && git commit -m "fix off-by-one in totals" # orphan commit git switch main # the fix "vanishes" ``` ## Your task 1. Confirm the fix is gone from every branch: `git log --all --oneline` shows no `fix off-by-one`. 2. Find the orphan commit: `git reflog` → locate the `commit: fix off-by-one in totals` entry → note its SHA. 3. Recreate the branch at that SHA: `git switch -c fix/off-by-one `. 4. Verify the content: `git log --oneline --graph` shows the rescued commit on a named branch; `cat report.py` contains the fix. 5. Write `RESCUE.md`: what detached HEAD means, how reflog located the orphan, the prevention rule (never commit detached; use `git switch -c`). ## Deliverables - Repo URL (submission notes). - `RESCUE.md` file upload. **Submission contract:** paste the repo URL into submission notes and upload `RESCUE.md`. Reviewer checks the rescued branch exists with the fix content, and the graph shows a clean topology. ## 100-pt rubric - Reproduce detachment + locate orphan via reflog (25) - Recreate branch at orphan SHA, verify content (25) - Explain detached-HEAD semantics correctly in RESCUE.md (20) - Graph shows clean topology (15) - Prevention rule stated (15)