Branch Merging in Git

Branch merging in Git is the process of combining changes made in different branches to integrate them into a single branch. This is essential for consolidating team work and finalizing features or bug fixes into the main branch of the project.

Types of Merging in Git

Git provides several ways to perform a merge. The two most common types are:

1. Fast-Forward Merge: This merge occurs when the target branch is directly behind the branch being merged. Git simply moves the pointer forward.
2. Three-Way Merge: This type of merge happens when the branches have evolved independently. Git will use three points: the last commits of each branch and their most recent common ancestor.

Preparing for the Merge

Before merging branches, it's recommended to ensure that the local history is up to date. To do this, perform a pull of the target branch:

bash

This ensures that the target branch is up-to-date with the remote repository.

Performing a Merge

To merge a branch into the current branch, use:

bash

Example:

Suppose you are in main and want to merge feature-xyz:

bash

This command merges feature-xyz into main.

Fast-Forward Merge

If main has not advanced since feature-xyz was created, Git will perform a fast-forward merge:

bash

Three-Way Merge

If both main and feature-xyz have had independent developments, Git will perform a three-way merge:

bash

Visualizing Merges

After a successful merge, you can visualize the commit history with:

bash

This command displays a graph of the commit history, making it easy to see branches and merges.

Aborting a Merge

If you encounter problems during the merge, you can abort it:

bash

This will revert the repository to its state before attempting the merge.

Handling Merge Conflicts

Sometimes, when Git cannot automatically combine the changes, merge conflicts occur. Merge conflicts must be resolved manually.

1. Identifying the Conflict: Git will mark conflicts in the affected files and indicate the conflicts when attempting a merge.
2. Resolving the Conflict: Edit the conflicting files to resolve the conflicts manually.
3. Adding Resolved Files: Once conflicts are resolved, add the files to prepare them for commit:

   bash
   

4. Finalizing the Merge with a Commit:

   bash
   

Summary

1. Prepare the branch for merging: git pull origin <target-branch>
2. Basic merge: git merge <branch-name>
3. Fast-Forward Merge: Occurs automatically if there are no divergent changes.
4. Three-Way Merge: Occurs automatically if there are divergent changes.
5. Visualization: git log --oneline --graph --all
6. Abort a merge: git merge --abort
7. Manually resolve merge conflicts

Performing a merge correctly is crucial to maintaining a clean and consistent project history. In the upcoming chapters, we will delve deeper into resolving merge conflicts and other advanced merging strategies.