Merge vs. Rebase Vocabulary Exercises

1 / 5

A team policy states: "Always squash commits before merging a PR."

What does squashing commits do to the Git history?

Squash merge strategies:

Strategy	Main branch history	Feature commits
Squash merge	1 commit per feature (clean)	Lost (compressed into one)
Merge commit	Merge commit + all feature commits	Preserved with merge bubble
Rebase merge	All feature commits (linear)	Preserved, new SHAs

Key vocabulary: squash merge, atomic commit, clean history, squash vs. merge commit vs. rebase.

2 / 5

A code review uses a merge commit strategy and the commit graph shows a "merge bubble".

What is a merge bubble and when is it preferred?

Merge commit (merge bubble) — preserving full context:

Feature	Detail
Two parents	Merge commit references both the branch tip and main tip
Non-linear history	Shows branch diverge and merge points visually
Preserve when	Audit trail matters; large reviewed features; release tracking

Compare: rebase = linear history (no bubble), squash = linear + compressed. Key vocabulary: merge commit, two parents, non-linear history, audit trail preservation.

3 / 5

A developer runs git rebase main on their feature branch.

What does rebasing onto main do?

git rebase — re-writing branch history onto a new base:

Before rebase	After rebase
Branch base: old main commit	Branch base: current main tip
Non-linear graph	Linear graph, enable fast-forward merge
Old commit SHAs	New commit SHAs (history rewritten)

Critical rule: NEVER rebase public/shared branches — it rewrites history and breaks collaborators. git push --force-with-lease needed after rebase. Key vocabulary: linear history, commit SHA rewrite, force-push after rebase, don't rebase public branches.

4 / 5

A code review comment says: "The merge was a fast-forward."

What conditions allow a fast-forward merge?

Fast-forward merge — possible only when no divergence exists:

Situation	Merge type needed
main has NO new commits since branch point	Fast-forward possible (pointer moves forward)
main HAS new commits since branch point	3-way merge needed (creates merge commit)

History stays perfectly linear with fast-forward. Use --no-ff flag to force a merge commit even when fast-forward is possible. Key vocabulary: fast-forward merge, branch pointer, linear ancestry, --no-ff flag.

5 / 5

A team needs to revert a feature that was merged with a squash. Why is reverting a squash merge easier than reverting individual commits?

Squash for reversibility — the rollback advantage:

Strategy	Revert process
Squash merge	`git revert <single-SHA>` — one command, done
15 individual commits merged	Identify all 15, revert in reverse order — or use `git revert -m 1 <merge_SHA>`

Squash = one commit = one natural atomic unit to revert. Key vocabulary: atomic revert, single-commit rollback, git revert vs. git reset, squash for reversibility.