**Course Title:** Version Control Systems: Mastering Git **Section Title:** Advanced Git Techniques **Topic:** Rebasing vs. merging: When to use each **Introduction** In Git, merging and rebasing are two powerful techniques used to integrate changes from one branch to another. While both methods achieve the same goal, they differ significantly in their approach and outcome. Understanding the differences between rebasing and merging is crucial for effective collaboration and maintaining a clean repository history. In this topic, we'll explore the concepts of rebasing and merging, discuss when to use each, and provide practical examples to illustrate the differences. **Merging** Merging is the most commonly used method in Git to integrate changes from one branch to another. When you merge two branches, Git creates a new "merge commit" that combines the histories of both branches. This commit has two parent commits: the tip of the current branch and the tip of the branch being merged. By default, Git uses the recursive merge strategy, which tries to find the common base between the two branches and applies the differences on top of that base. **Rebasing** Rebasing is an alternative to merging that integrates changes from one branch to another by rewriting the commit history. When you rebase a branch, Git reapplies each commit from the original branch on top of the target branch, creating a new series of commits that maintain the original commit messages and timestamps. **Comparison of Rebasing and Merging** Here are key differences between rebasing and merging: * **Repository History**: Merging creates a new merge commit, preserving the commit history of both branches. Rebasing rewrites the commit history, making it appear as if the changes were made on the target branch all along. * **Branch Identity**: Merging maintains the original branch identity, while rebasing rewrites the branch identity to reflect the changes. **Example: Merging vs. Rebasing** Let's say we have two branches, `feature` and `main`, and we want to integrate the changes from `feature` into `main`. We can use either merging or rebasing, as shown below: ```bash # Initial commit history A -- B -- C (main) \ D -- E (feature) # Merging git checkout main git merge feature B -- C -- F (main) / \ D -- E (feature) # Rebasing git checkout feature git rebase main B -- C -- D' -- E' (feature) ``` **When to Use Merging** Use merging when: 1. **Preserving commit history**: You want to keep the commit history of both branches intact. 2. **Collaborative workflows**: You're working with others and want to avoid rewriting commit history. 3. **Rebasing is not possible**: You're working with a lot of commits and can't afford to rebase the entire branch. **When to Use Rebasing** Use rebasing when: 1. **Linear commit history**: You want to maintain a linear commit history and avoid merge commits. 2. **Simple branching**: You're working alone or with a small team on a simple feature branch. 3. **Integration testing**: You want to review and test individual commits before integrating them into the main branch. **Conclusion** Rebasing and merging are both valuable techniques for integrating changes in Git. While merging preserves commit history and is suitable for collaborative workflows, rebasing provides a linear commit history and is ideal for simple branching and integration testing. By understanding the differences between rebasing and merging, you can make informed decisions when working with branches in Git. **Key Takeaways** * Use merging to preserve commit history and for collaborative workflows. * Use rebasing for linear commit histories and simple branching. **Practice Time!** Try the following exercises to practice rebasing and merging: 1. Create a new branch from `main` and commit a few changes. 2. Create a new branch from the first branch and commit more changes. 3. Merge the second branch into the first branch. 4. Rebase the first branch onto `main`. 5. Compare the resulting commit histories. **Need Help or Have Questions?** If you have any questions or need help with the exercises, feel free to ask in the comments below. **Further Reading** For a more in-depth explanation of rebasing and merging, check out the official Git documentation: [https://git-scm.com/docs/git-rebase](https://git-scm.com/docs/git-rebase) and [https://git-scm.com/docs/git-merge](https://git-scm.com/docs/git-merge). **Next Topic:** Stashing Changes: `git stash` and `git stash pop`.