What is git merge?

git merge is a command that combines changes from one branch into another, keeping the history of both branches.

In simple terms: "Take everything that was done in the other branch, and add it to the current one."

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#Why git merge is needed

In Git you usually work with branches:

• main / master, the main branch
• feature/*, branches for new features
• bugfix/*, branches for fixes

You work in a separate branch, and when everything is ready, you merge it back into the main one. That is exactly what git merge is for.

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#How git merge works

Example:

1. You are on the main branch
2. You want to bring in changes from the feature-login branch

Result:

• All commits from feature-login appear in main
• The branch history is preserved

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#What happens "under the hood"

Git:

1. Finds the common ancestor commit of the two branches
2. Compares the changes
3. Combines them
4. Creates a merge commit (if needed)

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#Types of merge

#1. Fast-forward merge

If main had no new commits, Git simply moves the pointer:

After the merge:

A---B---C---D---E (main)

No extra commits Clean history

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#2. Merge commit (a regular merge)

If both branches evolved in parallel:

Git creates a separate merge commit:

You can see that there was a separate branch The history is maximally honest

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#Conflicts during a merge

If the changes touch the same lines, Git does not know which to pick.

Then:

• Git reports a conflict
• You manually pick the correct option
• After that you run git commit

Conflicts are normal, this is emphasized at interviews.

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#Advantages of git merge

Simple to use Safe Does not rewrite history Good for team work

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#Disadvantages

The history can become "noisy" (many merge commits)

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#Short version for an interview

git merge is a command for combining branches that preserves history and creates a merge commit when needed. It does not rewrite commits and is considered safe for shared work.