Git offers two primary strategies for integrating changes from one branch into another: merge and rebase. Understanding when and why to use each is essential for maintaining a clean, navigable project history.
Git merge combines two branch histories by creating a new 'merge commit' that has two parent commits. It preserves the exact historical record of when branches diverged and when they were rejoined. Running `git merge feature` from your main branch produces a non-destructive operation that never rewrites existing commits. This makes it the safest integration strategy, especially on shared branches.
Git rebase moves or 'replays' a sequence of commits from one branch onto the tip of another, rewriting each commit with a new SHA hash. Running `git rebase main` from your feature branch re-applies your feature commits on top of the latest main, as if you had branched from that point. The result is a perfectly linear project history with no merge commits. Because commits are rewritten, rebase is considered a history-altering operation.
Merge produces a directed acyclic graph (DAG) history that accurately reflects parallel development, which can look complex in visualizers like `git log --graph`. Rebase produces a straight, linear history that is easier to read and bisect with `git bisect`. The trade-off is truthfulness versus readability — merge is honest about what happened, while rebase tells a cleaner but simplified story. Both approaches are valid depending on your team's workflow preferences.
Never rebase commits that have already been pushed to a shared public branch. Because rebase rewrites commit SHAs, any collaborator who has based work on those original commits will have a diverged history that is painful to reconcile. Rebase is safe when used exclusively on local or private feature branches before merging into a shared branch. Violating this rule is the most common source of serious Git confusion on teams.
Interactive rebase (`git rebase -i HEAD~N`) lets you squash, reorder, edit, or drop individual commits before integrating your work. This is widely used to clean up messy work-in-progress commits into a single, meaningful commit before opening a pull request. It gives you fine-grained control over what history gets recorded permanently. It is still subject to the golden rule — only rewrite commits that have not been shared publicly.
Use merge when integrating long-lived or shared branches (e.g., merging a release branch into main) to preserve the full historical context. Use rebase to keep a feature branch up to date with main during development, producing a cleaner pull request diff. Many teams adopt a hybrid: rebase locally to stay current and squash-merge pull requests into main for a linear trunk history. Agreeing on a consistent team convention is more important than which strategy you pick.
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