Git merge command tutorial

Git is a widely used version control system that allows multiple developers to collaborate on a project simultaneously. In the development process, it is common to have multiple branches to work on different features or fixes. As a result, merging those branches is an essential step to bring those changes together into one cohesive codebase. In this tutorial, we will explore the Git merge command, its usage, and its benefits.

What is Git merge command?

In Git, the merge command is used to combine the changes from one branch to another. Let’s say you have two branches, one is called feature_branch and the other is called master. When you are finished with your changes on the feature_branch, you can merge those changes into the master branch using the merge command.

The merge command finds the common ancestor of both branches and combines the changes made on both branches since this common ancestor. By merging a branch, you can ensure that any changes from that branch are included in the final version of the codebase.

How to use Git merge command?

The syntax for Git merge command is as follows:

git merge <source_branch>

Here, the source_branch is the branch from which you want to merge changes into your current branch.

Before you perform a merge operation, it is a good practice to ensure that your local branch is up-to-date with the remote branch. Therefore, it’s recommended to first fetch and pull changes from the remote branch using the following commands:

git fetch
git pull

Once you have pulled the latest changes from the remote branch, switch to the branch you want to merge into. Then, execute the merge command with the name of the branch you want to merge from. For example, to merge changes from the feature_branch into the master branch, the following commands can be used:

git checkout master
git merge feature_branch

If there are any conflicts between the two branches, Git will prompt you to resolve them manually. It’s important to address any conflicts effectively to ensure that there are no unexpected side effects in the merged code.

Git merge strategies

Git provides different merge strategies to handle merge conflicts. By default, Git uses the "recursive" merge strategy, which combines changes in the most efficient way possible. However, if you need more control over the merge process, you can use other merge strategies. Here are some of the most commonly used merge strategies:

Fast-forward merge

A fast-forward merge is the default Git behavior when merging two branches with a linear history. In this case, Git simply moves the pointer of the branch you’re currently on forward to the latest commit on the other branch. This type of merge is ideal for small changes that do not introduce conflicts.

For example, if you have a branch feature_branch that has three new commits on top of master, you can merge feature_branch into master using a fast-forward merge using the following commands:

git checkout master
git merge --ff-only feature_branch

Three-way merge

A three-way merge is the default Git merge strategy when merging two branches with divergent histories. In this type of merge, Git finds a common ancestor commit, then looks at the changes made on each branch since that commit, and combines them. This type of merge can result in conflicts, which must be resolved manually.

Recursive merge

A recursive merge is the default Git merge strategy for all other cases. It combines changes on both branches in the most efficient way possible by creating a new merge commit. Git uses heuristics to decide the best way to combine changes, but conflicts can still occur and must be resolved manually.

Octopus merge

An octopus merge is a merge strategy that can merge more than two branches into a single one. This is useful when you have multiple feature branches that have already been merged with the development branch, and you want to merge them all at once.

To perform an octopus merge, use the following syntax:

git merge branch1 branch2 branch3 ...

Conclusion

In conclusion, Git merge command is an essential tool to manage codebase changes and ensure a smooth development process. Merging changes from different branches allows developers to work independent of each other while still contributing to a single codebase. With this tutorial, you should now have a good understanding of Git merge command, its syntax, and merge strategies. Happy merging!