Introduction

• git merge command is used to combine the work from one branch into another, typically during development.
• The most common use case is merging a feature branch (like feature-xyz) into a main or development branch.
• It’s commonly used in collaborative environments when feature branches are finished and ready to be integrated into the main branch.
• Merging keeps the full history of changes from both branches.

• There are two types of merges:
  1. Fast-forward merge: Happens when the current branch has not diverged from the target branch.
  2. Three-way merge: Happens when both branches have diverged — Git creates a new merge commit.

How to use git merge ?

1. Open the Git terminal (or command prompt) and navigate to the project folder where your Git repository is initialized.
2. Create and Commit on a Feature Branch :-
   • Let’s assume you're on the default branch (main) and want to work on a new feature.
     • Create a new branch (if not created):
       • git branch feature-1
     • Switch to the new branch:
       • git switch feature-1
     • Make changes to your files, then add and commit them:
       • git add .
       • git commit -m "Implemented feature-1"
   • Below are the commands with output:
     
3. Switch Back to the Main Branch :-
   • Once your work on feature-1 is complete, switch back to the main branch:
   • • git switch main
4. Merge the Feature Branch into Main
   • Now, merge the feature-1 branch into main
     • git merge feature-1
       • The git merge command always merges the specified branch (i.e. feature-1) into your current branch (i.e. main).
       • If there are no conflicts, Git will create a merge commit automatically.
       • If there are conflicts, resolve them manually in the files. Then:
         • git add .
         • git commit
5. (Optional) Delete the Feature Branch
   • After successful merging, you can delete the feature branch:
   • git branch -d feature-1
6. Verify the Merge
   • Use this to check the branch list and confirm you’re on main
     • git branch
   • And view the merge history:
     • git log --oneline

• Below is the output of the above commands:
  • 

Different ways to use git merge ?

1. Merging a Local Branch into the Current Branch:
   • Syntax :
     • git merge <branch-name>
   • Example:
     • git merge feature-branch
   • Merges feature-branch into the currently checked-out branch.
2. Abort a Merge in Case of Conflict:
   • Syntax :
     • git merge --abort
   • If conflicts occur during merging, this command cancels the merge process.
3. Merging After Fetching from a Remote Repository (Most Common):
   • Syntax :
     • git merge origin/<branch-name>
   • Example :
     • git merge origin/main
   • Merges the latest changes from the remote main branch into your local branch after fetching updates.
4. Fast-Forward Merge (If No Diverging Changes Exist) (Commonly Used) :
   • Syntax :
     • git merge --ff-only <branch-name>
   • Exmaple :
     • git merge --ff-only origin/main
   • Merges the remote branch only if no conflicting changes exist.
5. Squash Merge (Combine Multiple Commits into One Before Merging) (Commonly Used for Clean History) :
   • Syntax :
     • git merge --squash <branch-name>
   • Example :
     • git merge --squash feature-branch
   • Combines all commits from feature-branch into a single commit before merging.