Git – Merge

Pre-requisite: Git 

Git is the most popular version control system which records the changes made to our project over time in a special database called a repository. We can look at our project and see who has made what changes when and why and if we screw something up we can easily revert our project back to an earlier state. 

What is Git Merge?

Git merge will help to combine the changes from two or more branches into a single branch. Developers will work on different branches to improve code or to develop the code after completion we can merge them into a single version of the code.

Note: Key Terminologies

• Current branch: The branch to be merged
• Target Branch: The branch in which we want to merge the current branch

How Does Git Merge Work?

The concept of git merging is basically to merge multiple sequences of commits, stored in multiple branches in a unified history, or to be simple you can say in a single branch.

What happens is when we try to merge two branches, git takes two commit pointers and starts searching for a common base commit in those two specified bit branches. When git finds the common base commit it simply creates a “merge commit” automatically and merges each queued merge commit sequence. There is a proper merging algorithm in git, with the help of which git performs all of these operations and presents conflicts if there are any.

In our case, we have two branches one is the default branch called “main” and the other branch named “dev” and this is how our git repo looks before merging. Here git finds the common base, creates a new merge commit, and merged them.

A git merge operation is performed by running the below command. When we perform merging, git always merges with the current branch from where we are performing the operation(in our case it is “main”). By this, the branch being merged is not affected.

 "git merge <name of the branch to be merged (in our case it is "dev")>". 

Merging Types

In Git, there are two primary types of merging. There are.

1. Fast-forward merging.
2. Three-way merging.

1. Fast-Forward Merging

Fast forward merge happens when the tip of the current branch (“dev” in our case) is a direct ancestor of the target branch (“main” in our case). Here instead of actually merging the two branches git simply moves the current branch tip up to the target branch tip. Fast-forward merge is not possible if the branches have diverged. Then we need a 3-way merge which uses a dedicated commit to merge two histories or you can say branches.

2. Three-Way Merging

When the base branch has changed since the branch was first created, this kind of merging takes place. Git in this situation generates a fresh merging commit that incorporates the modifications from both branches. Git compares the modifications made to both branches with those made to the base branch using a three-way merge process. Following that, it integrates both sets of changes into a single new commit.

Git also supports some other types of merging like recursive and octopus margin. With the help of a single merge commit “octopus merging” can merge multiple branches at once. “Recursive merging” is similar to three-way merging but it can handle some more complex merge operations than the three-way merging.

Essential Commands To Perform Git Merging 

First and foremost, we need a git repository with at least two branches in it in order to perform the git merge procedure. Any git repo has one default branch when it is first created (by using the “git init” command). So, we must first make another branch. To do this, we must execute the command below.

git branch <name of the branch you wanna create>

In our case the name of the branch is dev.

Here we have created two branches one is the default “main” and another is “dev”. We have also committed two changes in two branches.

Now to merge these two branches first we have to follow the below steps

• checkout to the target branch to merge the current branch
• then run the below command

git merge <name of the current branch>

Now we have successfully merged our two branches and as you can see we have the same changes or you can say commits in both branches.

Steps To Merge a Branch

To ensure that the merging process goes smoothly we need to follow a series of steps for merging which involves resolving any conflicts that we may face. Below are the basic steps involved.

Step 1: Creating a new branch.

Create a new branch from the remote repository branch which you want to merge. If errors are faced while merging we can go back to the previous version immediately.

Step 2: Make sure always latest changes are pulled.

Always make sure before merging the latest changes that the latest changes are pulled from both branches like the master and the branch you want to merge.

Step 3: Resolving the merge conflicts.

While merging the branches it is possible that some merge conflicts will be raised then git will prompt you to resolve the merge conflicts. If any merge conflicts are not raised then git will automatically merge the branches. 

Step 4: Merged code needs to be tested.

It is essential to test the merged code and we have to make sure that the code doesn’t have any bugs and it is working properly. To test the code we do it automatically or manually.

Step 5: Commit the merged code.

Once completing of merging the code if you are satisfied with the work, Know it’s time to commit the new changes of code into the new branch.

Step 6: Push the merged branch.

Lastly, make the new branch accessible to other team members by pushing it to the repository.

In conclusion, pulling the most recent changes, resolving conflicts, testing the merged code, committing the changes, and pushing the new branch are the essential phases in the Git merge preparation process. The merging procedure in Git can be streamlined and effective with careful planning and attention to detail.

How To Resolve Merge Conflicts?

While merging the two branches if changes are made to two different branches then git will not merge automatically it prompts the user to resolve the merge conflicts manually. Below are the steps to resolve the merge conflicts in git: 

Step 1: Identify the conflict files.

Git will automatically display a message by indicating the file to be resolved from merge conflicts. You have to resolve the conflicts manually.

Step 2: Open the conflict files.

Open the merge conflict files by using editors whatever you are convenient with like (IDE). After opening we can conflict markers as shown below it will indicate where the conflicts are located.

Conflict markers

(<<<<<<<, =======, and >>>>>>>) 

Step 3: Resolve the conflicts.

Remove the unnecessary changes after examining them carefully and keep the changes that are more important.

Step 4: Moving to the staging.

Use the git add command to add the updated files to the staging area after the conflicts have been resolved.

Step 5: Commit and Push the changes

After resolving conflicts commit the changes by using the below command.Including the message which gives information about changes made while resolving the conflicts.

git commit -m "message"

Push the changes made to the remote repository by using. Below command.

git push 

Where other developers can access the code. And perform any changes that are required.

After resolving the conflicts, it is crucial to carefully analyze and test the merged code to make sure that the modifications are functioning as intended and that no new problems have been introduced. These procedures can help developers resolve merge disputes in Git and maintain a dependable and stable codebase.

Git Merge vs Rebase

Git Merge	Git Rebase
Git merge will create a new commit by combining the changes in one branch with another branch.	Git rebase will integrate one branch commits to another branch by this the commit history will be rewritten.
The commit history of all the branches with which you have merged will be stored.	A new commit will be created when you integrate the changes.
It is useful for incorporating changes from a feature branch or integrating changes from multiple developers.	Rebase is also helpful for resolving conflicts early and maintaining a more streamlined and cohesive commit history.

Frequently Asked Questions 

1. What does git clean do?

Answer: 

It will delete untracked files in git working directory.

 run the rm command with the -f and -r switches to recursively remove the .git folder and all of the files and folders it contains.

2. How to remove all git data?

Answer: 

You can use rm command with the options like -f and -r to remove all the git data

Conclusion

In the last section, we went over how to step-by-step combine two branches into one branch. And we talked about different git versions, merging with examples, and how to address merge conflicts with step-by-step instructions. When two different branches make updates to the same line in a file, or when a file is destroyed in one branch but changed in the other, a conflict results. Working in a team environment will almost always result in conflicts.