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GISI ADO Level study materials
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GISI ADO Level: Version Control with Git

GISI ADO Level · Work through your exam, one topic at a time.

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Version Control with Git

Scope of this domain

Version Control with Git tests command-level understanding of Git's data model and judgement about history on shared branches: the three trees, branches as pointers, merge versus rebase, undo operations, and collaboration workflows such as trunk-based development versus GitFlow.

Core rules and concepts

  • Git stores snapshots, not diffs. A commit points to a tree and to parent commits; a branch is a movable pointer to a commit; HEAD points to the current branch.
  • Three trees: working directory, index (staging area), HEAD (last commit). git diff compares workdir to index; git diff --staged compares index to HEAD.
  • reset --soft moves HEAD only; --mixed also resets the index; --hard also overwrites the working directory, risking data loss.
  • revert creates a new commit that undoes an earlier one and is safe on shared history. reset rewrites history and needs a forced push.
  • Rebase replays commits onto a new base, producing new SHAs. Good for local cleanup, harmful on branches others have pulled.
  • --force-with-lease refuses to overwrite if the remote ref moved since your last fetch.
  • .gitignore affects only untracked files; already-tracked files need git rm --cached.
  • reflog records local HEAD movements and recovers commits orphaned by reset or rebase.

Worked example

A developer runs git reset --hard HEAD~2 on main after already pushing, losing two commits. Reasoning: locally, git reflog shows the pre-reset SHA and git reset --hard <sha> restores it. But because main was published, the correct remediation is to restore the commits and use git revert of the pushed commits, or re-push with --force-with-lease only if nobody has pulled. Rewriting published history breaks collaborators and CI caches.

Traps that cost marks

  • Believing rebase moves commits; it copies them with new SHAs.
  • Assuming cherry-pick preserves the original SHA.
  • Using reset on a shared branch instead of revert.
  • Forgetting that pull equals fetch plus merge or rebase depending on config.
  • Deleting a branch with unmerged work without checking reflog.