Git Rebase Vs Merge - What's the Difference? -Scaler Topics

Pre-requisite

Before delving into the differences between the git rebase and git merge commands, there are some prerequisites to consider:

Version Control Systems (VCS): VCS are essential tools in software development that track code and document changes. There are two main types: Centralized Version Control Systems (CVCS) and Distributed Version Control Systems (DVCS).
Git: Git is a widely used, free DVCS that tracks changes in code and project information. It can be operated via the command line (Git Bash) or a graphical user interface (Git GUI). Git saves project states as “commits,” allowing developers to track changes and revert to previous states if needed.
Branching: Branches in Git are independent lines of development used for adding features or fixing bugs without affecting the main project. Developers can work on new features concurrently and merge them back into the main project when completed.

With these foundational concepts in mind, let’s explore the differences between the git rebase and git merge commands.

Introduction

Git merge and git rebase are two methods for integrating changes from one branch into another. The key distinction is that git merge combines commits in a branch, preserving its history and merging all changes at once, while git rebase restructures the commit history, creating a linear sequence of commits. Git merge is suitable for larger teams where preserving branch history is important, while git rebase is preferred in smaller teams or single developer scenarios, as it simplifies the commit history by compressing changes into a single stream. Choosing the appropriate method depends on team size and the desired commit history structure..

Git Rebase

The git rebase command is used to move the feature branch to the tip of the master branch. The git rebase command is an alternative to the git merge command which is also used to merge or combine two branches. The git rebase command makes the commits be merged linearly, on the other hand, the git merge command will merge the commits in a time altogether. Git also provides an interactive merging. The git interactive rebasing is a tool that is used to edit, reorder, rewrite, etc. the current commits. We can only perform the interactive git rebasing on the current branch. The rebase command will check the root commit and perform a series of commits one after the other at the tip of the master branch commit. Git also provides us the advanced rebasing option, we can use the --onto command along with the rebase to activate a more powerful git rebasing.

Suppose we have an ongoing project and we have created another branch (namely the test branch) for the development process. We have some commits made in the master branch as well as in the test branch. Now we want to rebase the commits of the test branch to the master branch, we can run the following git rebase command.

Now if we want to continue with the changes made then we can run the command:

On the other hand, if we are not happy with the current change and we want to ship this change, then we can run the command:

Git Merge

Git merge is used to merge multiple commits of various branches into a single branch. We perform branching for parallel development of new feature(s) and bug fixing. Once the bug is fixed or the new feature is added, we can merge these branches into a single branch. The git merge command can also be considered as an alternative to the git rebase command which is also used to merge branches. For merging branches, git takes the head points of the commits and it will first find the common base commit among the branches and will perform a merge commit to combine the changes of each commit sequence. There are five types of merges in git, they are: Fast Forward, Recursive, Ours, Octopus, Resolve, and Subtree.

Suppose a master branch is there in the production and we have created other branches. Now, if we create some commits in the newly created branch (let's say the feature branch) then git will create new pointers to these commits for tracking changes.

Since the latest commits of the feature branch are ahead of the commits of the master branch, so we can use the git merge command to merge the commits of the feature branch to the `master branch.

Key Difference Between Git Rebase Vs Merge

The main difference between Git rebase and Git merge lies in their approach to integrating changes from one branch into another. Git merge combines the commits from a source branch into a target branch, preserving the original branch’s commit history. In contrast, Git rebase moves the entire commit history of the source branch onto the tip of the target branch, resulting in a linear, cleaner history that appears as if the changes were made directly on the target branch. The choice between rebase and merge depends on the desired branch history and workflow, with rebase often favored for its cleaner, more streamlined commit history.

Git Rebase Vs Git Merge

Let us now discuss git rebase vs merge commands.

Git Rebase	Git Merge
The git rebasing is performed linearly.	Git merging is done simultaneously as a single commit
The git rebase command creates an easily understandable history.	Git merge command also creates history but in a graphical form that can be hard to understand.
The git rebase command provides us with several options before merging.	Git merge command does not provide us with several options before merging.
The git rebase is used to deal with severe options of merging.	Git merge command merges two safe branches.
We should not use the git rebase command on public branches.	We can use the git merge command on both private and public branches.
The git rebase command rewrites the merging history.	The merge command preserves the merging history.
The git rebase command shows us the merge conflicts one after the other.	The git merge command shows us the merge conflicts altogether.
The git rebase command does not create any commit at the time of rebasing.	The git merge on the other hand creates a final commit at the time of rebasing.
Git rebase alters commit history, making it appear as if changes were made sequentially on the target branch.	Git merge creates a new merge commit, preserving the original commit history.
Interactive rebasing allows developers to squash or edit commits before merging, offering precise control over commit history.	Merging does not provide the same level of control over individual commits before integration.

Potential Drawbacks of the Two Operations

As we know that when we use the git rebase command, the history of the commit is rewritten on the other hand, if we use the git merge command then the history of the commit is preserved. Both of these commands must be used with care. Let us now look at some of the drawbacks of the two operations.

Merge conflict: Merge conflict is an issue that arises when we try to merge two branches that have been edited at the same time and in the same file (refer to the image provided below for more clarity), then git will not be able to merge them as git cannot identify the version that needs to be used for changes.

In case of a merge conflict, Git stops the merging process just before performing the merge conflict so that the user can resolve the conflict manually.

Published Branches: Another problem may arise when we have rebased our branch and have already published the branch remotely as well as someone else has also based their work on the branch. In such a scenario, git gets confused and will show that the branch is both ahead and behind at the same time.

We can use the git pull --rebase command to pull the remote changes to solve the problem.

We have previously discussed the issue related to merging and rebasing. Let us look at some of the rules or steps that need to be followed before performing git rebase or git merge.

Confirm the receiving branch. We will first check whether the HEAD of the branch is pointing to the correct merging branch or not. The checking can be performed using the git status command that is used to check the status of the repository. If we need to change the branch, we can use the git checkout command to move to a certain branch.
Fetch the latest remote commits. Before merging the branches, we need to first check if our receiving branch is up-to-date with the latest changes in the remote repository. For fetching the latest changes (to update the current branch), we can use the git fetch command. After fetching, we will use the git pull command to ensure that our master branch has the latest updates.
Rebase or Merge After performing the above steps, we can now initiate the merging by using the git rebase or `git merge command.

Conclusion

The choice between Git Rebase and Git Merge depends on a fundamental trade-off: preserving branch history or achieving a cleaner, linear commit history.
Git Merge is ideal for scenarios where preserving the original branching structure is crucial, making it a preferred choice for larger development teams.
Git Rebase offers a more streamlined and linear commit history, making it advantageous for smaller teams or individual developers.
Understanding the nuances of these Git operations and following best practices is essential for optimizing version control workflows.
Ultimately, the decision between Git Rebase and Git Merge should align with the project’s specific needs and the desired commit history structure.

Git Rebase Vs Merge - What's the Difference?