Merge Strategies in Git

Understanding merge strategies in Git can simplify your workflow, resolve conflicts efficiently, and ensure seamless collaboration among team members. In this article, we’ll explore various merge strategies, their use cases, and best practices for effective branch management.

What is a Merge in Git?

A merge in Git is the process of integrating changes from one branch into another. This is a common practice in collaborative projects where multiple developers work on different features or bug fixes in separate branches. Merging helps combine their efforts into the main branch, usually known as main or master.

Common Merge Strategies

Git provides several merge strategies, each suited for different scenarios. The choice of strategy depends on the complexity of changes and the desired outcome. Here are the most commonly used merge strategies:

1. Fast Forward Merge:

Fast-forward merge occurs when the target branch has not diverged from the source branch. In this case, Git simply moves the target branch pointer to the latest commit in the source branch. This strategy is simple and keeps the commit history linear.

Fast-forward merge

In this most commonly used merge strategy, history is just one straight line. When you create a branch, make some commits in that branch, the time you’re ready to merge, there is no new merge on the master. That way master’s pointer is just moved straight forward and history is one straight line.

Command:

git checkout main
git merge feature-branch

2. Recursive Merge:

Recursive merge is Git’s default strategy for non-trivial merges. It handles cases where branches have diverged by creating a new merge commit. This commit records the combined changes from both branches, preserving the history of both lines of development.

Recursive Merge

In Recursive merge, after you branch and make some commits, there are some new original commits on the ‘master‘. So, when it’s time to merge, git recurses over the branch and creates a new merge commit. The merge commit continues to have two parents.

Command:

$ git merge--no-ff

Note: There is nothing right or wrong of either one of the strategies but with fast forward merge you have a straight line of history and with the recursive merge, it is of multiple lines.

Fast-Forward merge vs Recursive merge:

Fast Forward	Recursive
No new commits on the master	New commits on the master
Linear History	Commit 2 parents
No merge commits	Merge commit is created
git rebase	git merge–no-ff

3. Octopus Merge:

Octopus merge is used for merging more than two branches simultaneously. It’s less common and typically used for automated merges involving multiple feature branches.

Octopus Merge

Octopus Merge strategy resolves cases with more than two heads but refuses to do a complex merge that needs manual resolution. It is primarily meant to be used for bundling topic branch heads together. This is the default merge strategy when pulling or merging more than one branch.

Command:

$ git merge -s octopus

4. Three-Way Merge

A three-way merge involves comparing three commits: the two branch tips and their common ancestor. Git uses this information to create a new merge commit that restore the differences.

Use Case: Useful when dealing with more complex merges involving multiple branches and several changes.

5. Squash and Merge

Squash and merge squashes all the commits from a feature branch into a single commit before merging into the target branch. This strategy simplifies the commit history, making it easier to follow.

Use Case: Ideal for merging feature branches with numerous small commits, resulting in a cleaner main branch history.

git checkout main
git merge --squash feature-branch
git commit -m "Merged feature-branch with squash"

6. Rebase and Merge

Rebase and merge rewrites the commit history of the feature branch, placing it on top of the main branch before merging. This results in a linear commit history without merge commits.

Use Case: Suitable for maintaining a clean and linear project history, especially in projects with strict commit guidelines.

git checkout feature-branch
git rebase main
git checkout main
git merge feature-branch