Git Rebase vs. Git Merge

Both git rebase and git merge integrate branch changes, but with fundamentally different approaches to commit history.

Key Differences & Scenarios

git merge integrates changes by creating a new merge commit. This explicitly records the combination of two divergent histories, preserving a complete, non-linear progression. It's non-destructive and ideal when retaining the exact historical context of all branch points is crucial, like combining a completed feature into main after main has progressed.

In contrast, git rebase rewrites commit history. It reapplies a series of commits on top of a different base, creating a linear, cleaner project history. This is often preferred for cleaning up local, unpushed history, making your branch appear as if it started from the latest main commit without messy merge commits.

Visualizing the Impact

Imagine commits as nodes and branches as lines connecting them.

Initial State (Merge & Rebase): main has A-B-C. feature-branch diverges from C, adding D-E.

A -- B -- C (main)

D -- E (feature-branch)

After git merge: A new merge commit (M) is created on main, with two parents (C and E). This shows a clear "Y" or "V" shape where histories converged.

A -- B -- C ---- M (main)
           \    /
              D ---- E (feature branch)

After git rebase: Commits D and E are "cut" and "pasted" as new commits (D', E') on top of main's latest commit. feature-branch then points to E', resulting in a linear history.

A -- B -- C -- D' -- E' (main, feature-branch)

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Git Fetch vs. Git Pull

git fetch and git pull interact with remote repositories, but differ in how they integrate changes locally.

Key Differences & Scenarios

git fetch is a "download-only" command. It retrieves new data (commits, branches) from a remote and updates your local remote-tracking branches (e.g., origin/main). It does not alter your local working directory or active branch, allowing you to review remote changes safely before integration. This is perfect for staying informed about team progress without immediate impact on your current task.

Conversely, git pull combines git fetch with an immediate integration (typically git merge) into your current local branch. This automates bringing in remote changes directly. It's suitable when you're confident accepting all remote changes to quickly update your branch before starting new work.

Visualizing the Impact

Understanding the "fetch then integrate" nature of git pull is key.

Initial State (Local & Remote Aligned):

Local: A -- B (main) Remote: A -- B (origin/main)

Remote Changes Occur: Teammate pushes new commit C to remote.

Local: A -- B (main) Remote: A -- B -- C (origin/main)

After git fetch: Downloads C, updates origin/main. Your local main remains untouched.

Local: A -- B (main) Remote: A -- B -- C (origin/main) <-- C is now known locally

After git pull (from "Remote Changes Occur" state): Fetches C, then merges C into your local main.

Local: A -- B -- C (main) Remote: A -- B -- C (origin/main)

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Git Reset vs. Git Revert

Both git reset and git revert undo changes, but git reset modifies history while git revert creates new history.

Key Differences & Scenarios

git reset directly rewrites history by moving your branch's HEAD pointer. This discards subsequent commits, making it powerful and potentially destructive. It's best for undoing local, unpushed changes (e.g., erasing a bug-ridden local commit before pushing). Use --hard with extreme caution as it discards uncommitted changes too.

git revert creates a new commit that undoes the changes of a previous commit. It does not rewrite history but adds an explicit reversal, preserving a clear audit trail. This is the safe method for undoing changes on shared branches that have already been pushed, as it avoids disrupting collaborators' histories.

Visualizing the Impact

Initial State (Reset & Revert): your-branch: A -- B -- C -- D

A -- B -- C -- D (HEAD -> your-branch)

After git reset --hard B: Your branch's HEAD moves to B. Commits C and D are effectively "removed" from history.

A -- B (HEAD -> your-branch) [C and D are now unreachable by this branch]

After git revert C: A new commit (C_revert) is created on top of D, reversing C's changes. Both C and D remain, with C_revert explicitly showing the undo action.

A -- B -- C -- D -- C_revert (HEAD -> your-branch)

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Conclusion

Mastering these core Git commands provides the flexibility and control necessary for efficient and collaborative development. Choose the right tool for the job to maintain a clean, understandable, and robust project history. Your understanding of these distinctions empowers you to navigate complex Git workflows with confidence.