Hands-On Git & GitHub Labs

Reading about git reflog and using it while your branch appears to have vanished are different experiences. These labs exist to make the second one familiar.

Each is a scenario you build yourself in a disposable repository, break deliberately, and repair — with the commands, the expected output, hints if you get stuck, and an explanation of why the fix works.

How the labs work

Everything runs locally, in a directory you throw away. Nothing touches a repository that matters. Where a lab needs GitHub, it says so and a scratch repository is enough.

No arbitrary code executes on our servers. There is nothing to sign up for and nothing to install beyond Git itself.

Each lab is self-contained — scenario, objective, prerequisites, starting state, tasks, hints, solution, explanation. Read the solution if you are stuck; the explanation is where the value is.

Tip

Try each task before reading its hint, and each hint before the solution. The labs are built so that the recovery command is the last thing you reach for, because that is the order you will face it in reality.

Git recovery

Work that appears lost, and the mechanisms that get it back.

01. Recover a deleted Git branchDelete a branch with unmerged work and recover it from the reflog. 10 minutes, beginner.

07. Recover a lost commitCommit on a detached HEAD, switch away, and get it back — and read the warning Git printed. 10 minutes, beginner.

08. Undo a bad mergeReset if nobody saw it, revert if they did — and the trap when you try to merge again. 15 minutes, intermediate.

09. Reset, revert and restoreFive situations, three commands, one that destroys work. 20 minutes, beginner to intermediate.

18. Bisect a regressionLet git bisect run the test and name the bad commit in three steps. 15 minutes, intermediate.

19. Recover from a force pushRestore a colleague's overwritten commit from a remote-tracking reflog. 20 minutes, intermediate.

Workflows

Merging, rebasing, and repairing them when they go wrong.

02. Resolve a merge conflictCreate a genuine conflict, read the markers correctly, resolve and abort. 15 minutes, beginner.

03. Repair a broken interactive rebaseMultiple conflicts, continue, skip, abort, and reflog recovery. 20 minutes, intermediate.

10. Parallel work with worktreesHandle a hotfix mid-feature without stashing or switching. 15 minutes, intermediate.

20. Interactive rebase cleanupFive messy commits into two reviewable ones, with the diff proving nothing changed. 15 minutes, intermediate.

GitHub

Routing review and setting the rules a pull request must satisfy.

11. Configure CODEOWNERSPredict the routing from the file alone, then verify on GitHub. 20 minutes, intermediate.

12. Design a pull request workflowTemplate, checks, review policy, merge method and rules — decided together, then tested. 30 minutes, intermediate.

CI/CD

Diagnosing pipelines that fail for reasons the error message does not name.

04. Debug a failing GitHub Actions workflowFour failures with misleading symptoms: merge base, permissions, skipped checks, cache keys. 25 minutes, intermediate.

13. Build a Python CI pipelineLint, test, matrix and cache — every stage run locally first. 25 minutes, intermediate.

14. Build a Node.js CI pipelineLockfile, npm ci, and the built-in test runner. 20 minutes, intermediate.

15. Build a Docker CI pipelineMulti-stage build, and the test stage that silently never ran. 30 minutes, intermediate to advanced.

Security

The workflow patterns that hand credentials to strangers.

05. Secure an unsafe GitHub Actions workflowAudit and fix four real vulnerability classes in one workflow. 30 minutes, advanced.

16. Migrate secrets to OIDCReplace a long-lived cloud key with a per-run token, and a trust policy that actually restricts. 35 minutes, advanced.

DevOps

Infrastructure change as a reviewable commit.

06. Ship an infrastructure change through a pull requestDeclarative manifest, plan on the PR, review checklist, promotion, reconciliation. 30 minutes, advanced.

17. Terraform pull request workflowPlan on the PR, and catch the one-number change that destroys a resource. 30 minutes, advanced.

Suggested order

The labs stand alone, but they build. Three tracks:

Git recovery and repair — 01 → 07 → 09 → 02 → 08 → 03 → 20 → 10 → 18 → 19. Establishes that Git rarely loses committed work, then works through conflicts, bad merges and rebases, and finishes with worktrees as the way to avoid half the problems.

GitHub and CI — 11 → 12 → 13 or 14 → 15 → 04. Routing and rules first, then a pipeline for your language, then packaging, then debugging one that has gone wrong.

Security and infrastructure — 05 → 16 → 06 → 17. Making a pipeline safe, removing the long-lived credential, then applying review discipline to infrastructure.

If you are new to Git, start at 01. If you are here for CI security, 05 stands alone.

Where to go next

Learning pathsA sequenced route through the curriculum for where you are now.

Git TroubleshootingA decision tree for the situation in front of you.

Git Command AtlasSearchable command reference with the caveats that matter.

Free cheat sheet bundlePrintable references for commands, recovery, review and security.

Modern Git Weekly

One advanced Git/GitHub technique, one practical workflow, and one security lesson every week.

New labs are announced in the weekly email, with the lesson they practise.

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