Cherry-pick and Reflog¶
Overview¶
Cherry-pick a hotfix commit onto another branch and use reflog to find a “lost” commit after a reset.
This is a core tutorial in Module 7 · Rebasing & History of the REBASH Academy Git for Cloud & DevOps Engineers series — written for Cloud, DevOps, Platform, and SRE engineers.
Prerequisites¶
Learning Objectives¶
By the end of this tutorial, you will be able to:
-
git cherry-pick <sha> - Read
git reflog - Recover a reset commit
Architecture¶
This topic’s control points and relationships are shown below.
Theory¶
What¶
Cherry-pick copies the changes from an existing commit onto your current HEAD as a new commit (new SHA, usually same message/patch). Reflog is a local diary of where HEAD and branch tips pointed — a recovery tool after reset, rebase, or detached-HEAD mistakes.
Why¶
Hotfixes sometimes land on a release branch and must be copied to main (or the reverse) without merging the whole branch. Reflog saves “lost” commits that still exist as objects after a bad reset. Together they are essential production safety nets.
How it works¶
git cherry-pick <sha> applies that commit’s diff to the current tree and creates a new commit. Conflicts pause the operation like merge/rebase. Ranges and -x (note the source SHA in the message) appear in advanced workflows. Reflog entries live under .git/logs and expire eventually; git reflog then git switch -c recover/<name> <sha> resurrects work. Reflog is not pushed to remotes — recovery is per clone.
Key concepts¶
| Tool | Mental model |
|---|---|
| Cherry-pick | Duplicate a patch as a new commit |
| Reflog | Local pointer history |
| GC grace | Objects linger until garbage collection |
| Duplicate commits | Same change, different SHAs after pick |
In release engineering, cherry-pick is common when a single fix must land on main and on a maintained release branch without merging unrelated commits. Document the source SHA in the commit message (or use -x) so future readers can see the lineage. Teach every on-call engineer git reflog before they need it in an incident.
Common pitfalls¶
- Cherry-picking merge commits without understanding parent selection
- Assuming reflog on a CI runner will save laptop mistakes
- Cherry-picking large unrelated commits instead of merging/rebase
- Waiting weeks to recover — expired reflog entries vanish
Hands-on Lab¶
Create a workspace for this tutorial.
Focus: cherry-pick a commit and recover via reflog
Step 1 – Cherry-pick across branches¶
git init
git config user.name "REBASH Learner"
git config user.email "learner@rebash.local"
echo main > a.txt && git add a.txt && git commit -m "chore: main"
git switch -c feature/hotfix
echo fix > fix.txt && git add fix.txt && git commit -m "fix: critical hotfix"
HOTFIX=$(git rev-parse HEAD)
git switch -
git cherry-pick "$HOTFIX"
git log --oneline -n 5
Step 2 – Recover with reflog after hard reset¶
echo oops > oops.txt && git add oops.txt && git commit -m "chore: oops"
OOPS=$(git rev-parse HEAD)
git reset --hard HEAD~1
git reflog -n 8
git cherry-pick "$OOPS"
git log --oneline -n 6
Final step – Cleanup note¶
Validation¶
- Lab commands run under
~/rebash-git/module-07-cherry/ - You can explain each Theory section in your own words
- You used modern tooling where it applies to this topic
- You can describe one production failure mode for this topic
Code Walkthrough¶
Production practice for Cherry-pick and Reflog always combines:
- Inspect before you change (status, plan, logs, dry-run)
- Prefer reversible, documented changes (Git, IaC, drop-ins, version pins)
- Capture evidence (command output, pipeline logs) for handovers
- Prefer current tools and APIs over legacy shortcuts
- Least privilege — escalate credentials only when required
Keep runbooks short enough to follow under pressure. Automate checks; keep humans for judgement.
Security Considerations¶
- Treat credentials and tokens for git as privileged — never commit them
- Prefer short-lived auth (OIDC, roles, SSO) over long-lived keys
- Validate blast radius before apply/deploy/delete operations
- Restrict who can approve production changes
- Collect audit logs; limit who can read sensitive traces
Common Mistakes¶
Cherry-picking merge commits without understanding parent selection
Validate assumptions against the Theory section and official docs before changing production.
Assuming reflog on a CI runner will save laptop mistakes
Lab shortcuts (open security groups, admin roles, skip approvals) must not ship unchanged.
Changing production without a rollback path
Always know how to revert (previous artefact, prior release, state rollback, DNS failback).
Best Practices¶
- Encode Cherry-pick and Reflog changes as code and review them in pull requests
- Pin versions (images, modules, actions, provider plugins)
- Separate environments with clear promotion gates
- Alert on symptoms with runbooks attached
- Destroy lab resources; tag everything with owner and expiry where possible
Troubleshooting¶
| Symptom | Likely cause | Fix |
|---|---|---|
| Auth / permission denied | Wrong identity, policy, or scope | Check caller identity, roles, and least-privilege policies |
| Timeout / no route | Network, DNS, security group, or endpoint | Trace path, DNS, and allow-lists before retrying |
| Drift / unexpected plan | Manual change or wrong state/workspace | Reconcile desired vs actual; avoid click-ops on managed resources |
| Pipeline/job red | Flaky step, cache, or missing secret | Read failing step logs; bisect recent workflow/config changes |
| Cost spike | Idle load balancer, NAT, oversized compute | Inventory billable resources; stop/delete labs promptly |
Summary¶
Cherry-pick and Reflog is essential for Cloud and DevOps engineers working with git. Practise the lab until the inspection and change path is muscle memory, then continue the track.
Interview Questions¶
- When is cherry-pick better than merging a whole branch?
- What does reflog record that git log does not?
- Cherry-pick conflict handling?
- How long is reflog kept by default roughly?
- Dangers of cherry-picking the same fix twice?
Sample answer — question 2
Use git reflog to find the pre-change HEAD and cherry-pick or branch from that SHA.
Sample answer — question 4
Cherry-picking hotfixes into multiple release branches needs clear tracking to avoid duplicate fixes.