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Many developers depend on the open-source code management system, Git. From sharing codes to editing specific features of an already deployed program, Git makes life easier in many ways. Two of the most used commands are Git merge and Git rebase. They serve the same end goal, integrating changes from multiple developers into one entity but are critically different.
This article focuses on the differences between the two commands, their application, and the merits and demerits of each. But before we look into the full comparison, let’s explain three important terms we shall refer to throughout the article: commit, branch, and merge.
Commit
A commit is basically the location where a code and the changes made to the code are stored in Git. For example, if a developer saves three Python files on Git, the files are grouped into one commit and assigned a commit ID number. When the developer or another developer makes changes to the code by adding more Python files, the changes are saved in a different commit and with a new ID. Simply put, every change on Git generates a commit.
Branch
A branch is an isolated version of code. There are two types of branches on Git: the master branch and the feature branch. Take, for example, a website; the master branch is where the code for the deployed site is stored, usually by default.
If a developer wants to add a feature to the website, they will copy the entire code into a different “folder” where they can do the tinkering without affecting the site. This “folder” is called a feature branch on Git. Once done, the developer then “merges” the feature branch and the master branch so that the changes on the former reflect on the latter.
Merging
On Git, merging is the process of including the changes of one branch into another branch. It can be done in two ways, Git merge and Git rebase.
Now, let’s compare these two methods.
Git Merge vs. Rebase: A Side-by-Side Comparison
| Git Merge | Git Rebase | |
|---|---|---|
| Working | Merges different Git branches | Integrates changes on one branch into another |
| Action on Commits | All commits on the feature branch are combined into one commit on the master branch | The same number of commits on the feature branch is added to the master branch |
| Logs | Preserves history of the commits | Rewrites the history of commits |
| Usage | Used on a shared branch | Used on a private branch |
| Suitability | Suitable for projects where the shared branch is not very active | Ideal for a very active main branch |
| Structure | Forms a chain-link structure | Forms a linear structure |
| Single Line Command | Git merge feature main | Git rebase main |
Git Merge vs. Rebase: What’s the Difference?
Now, let’s define these two techniques and elaborate more on how they differ from each other.
Git Merge: Definition
This is one of the merging techniques on Git. It keeps the commit logs on the feature branch intact while creating a new commit on the main branch.
Take, for example, a case where the main branch has commits 1, 2, and 3, and the feature branch has commits X and Y. When the developer performs a Git merge, the feature branch remains, but on the main branch, then two commits merge to form a commit 4. In doing this, the logs of the changes remain on the feature branch.
Git Rebase: Definition
It is a merging technique that integrates the feature branch on the master branch by creating individual commits for each commit from the feature branch. It then gets rid of the feature branch.
For instance, for a main branch with 3 commits and a feature branch with X and Y commits, the Git Rebase command will add commits X and Y onto the main branch as commits 4 and 5, then discard the feature branch. As a result, it leaves no evidence of the existence of the feature branch.
The main difference between the two is how they handle commit history. While Git Merge joins the histories of two or more changes into a chain-link-like structure, Git rebase reapplies these changes onto the main branch without preserving their history, giving the impression of a linear log.
Merits of Git Merge and Rebase
The Git Merge command preserves the existing branches leaving a history of all logs. It is also simple, straightforward, and easy to use. In fact, it was the first type of merging used on Git, which explains why it retains the “merge” in its name.
Since Git Merge gives a chronological order of changes and provides the context of the changes, other developers can get the bigger picture of when and how each change occurred. This not only makes the development process easy to follow through but also makes it easy to find and correct mistakes.
On the other hand, Git Rebase rewrites the history of the changes in the code; as a result, it simplifies what could otherwise be a complex history by combining intermediate commits into one. Its linear structure reduces clutter while also minimizing the commit noises common in busy branches and repositories.
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Demerits of Git Rebase and Git Merge
By keeping the history of all the changes, the Git Merge results in an exhaustive Git log that gets messy and unhelpful if not properly maintained. It is not very user-friendly, especially where the main branch is active.
Git Rebase command, on the other hand, is meant to solve these demerits of Git Merge, which it does. However, it also presents its own share of drawbacks.
It minimizes the feature commits into smaller commits on the main branch it creates, making it impossible for other developers to know when and how the changes were made.
The other drawback is the resolution of conflicts. On Rebase, you must resolve conflicts in the order in which they were created, and as a result, you fix them one by one, unlike all at once, as with Git Merge.
Finally, Git Rebase does not honor pull requests, which is the command for seeing minor changes made by another development team member.
It is, however, possible to avoid some of the common issues with the Git Rebase command:
- Avoid using the rebase command on a remotely-published branch unless you are certain that no one else is working on the branch.
- Create a backup of the branch you are about to rebase before rebasing it. It will make it easy for you to compare the changes and, if necessary, go back to the pre-base state.
Git Merge vs. Rebase: 4 Must-Know Facts
- Git Merge adds the contents of the feature branch onto the base branch without discarding the feature branch hence keeping the history of changes.
- Rebasing discards the feature branch and its related history.
- Rebase moves the feature branch to the tip of the main branch but gives its content new ID numbers.
- Git Rebase is more complex to undo than Git Merge.
Git Merge vs. Rebase: Which is Better? Which One Should You Use?
At some point, you will have to choose between one of these branching strategies, so which one should you go for? Well, the answer to that depends on one key factor: your team.
- Small teams: If working on the project alone or in a small team, then Git Rebase is a good choice. However, Git Merge would be a better option for large groups.
- Transparency: Is there a need to track all the changes made by every developer? If transparency is needed, even if working alone, Git Merge is the command to use.
- Log access: Just as for transparency, Git Merge is the strategy to go for; it is necessary that the others on the team understand where each commit came from. However, in case there is a need to make such logs inaccessible, use Git Rebase. It is a suitable option when working on branches you do not want other team members to see.
Using Both Git Merge and Git Rebase
Often most Git-savvy developers use these techniques in the same project.
Consider a 3-branch scenario: a main branch, a feature branch, and a sub-branch of the feature branch. A developer can make changes to the sub-branch and then rebase it to the feature branch before using Git Merge to merge the feature branch onto the main branch. This way, other developers can only see the changes the developer made on the feature branch but will never see what was done on the sub-branch of the feature branch. Simply put, you can use Git Rebase on a private branch and then integrate all the commits onto the main branch using the Git merge command.
Other Considerations
A good branching strategy should allow the developers to work at their own pace and only add what makes sense to the main timeline. To achieve this, it is important to have the developers work on isolated parallel teams that use Git Rebase at the individual level and Git Merge at the team level or the main branch.
The level of Git competencies of the team is also an important consideration. Those with only the basics should stick to the Git Merge command or learn the nuances of Git Rebase before applying it to the project.
Therefore, the decision on whether to use Git Merge or Git Rebase lies not on whether one strategy is better than the other but on the dynamics of the development team. Level of Git competency, organization structure, goals, and team philosophy are the crucial determinants.
