Merge strategies overview in Git - Mini Project: Build & Apply

Merge strategies overview

📖 Scenario: You are working on a project with two branches: main and feature. You want to learn how to combine changes from feature into main using different merge strategies in Git.

🎯 Goal: Learn how to use three common Git merge strategies: merge, rebase, and fast-forward. You will practice creating branches, making commits, and applying these merge strategies step-by-step.

📋 What You'll Learn

Create a Git repository with two branches: main and feature

Make commits on both branches

Use git merge to combine branches with a merge commit

Use git rebase to replay commits from one branch onto another

Use git merge --ff-only to perform a fast-forward merge

💡 Why This Matters

🌍 Real World

In real projects, developers use different merge strategies to keep the project history clean and understandable. Knowing when to use merge commits, rebase, or fast-forward merges helps teams collaborate smoothly.

💼 Career

Understanding Git merge strategies is essential for software developers, DevOps engineers, and anyone working with version control. It helps in managing code changes, collaborating with teams, and maintaining a clear project history.

1

Setup initial Git repository and branches

Initialize a Git repository. Create a file named README.md with the content Initial commit. Commit this file on the main branch. Then create a new branch called feature from main.

Git

# Initialize Git repository and create branches
# Your code here

Hint

Use git init to start the repo. Use echo to create the file. Use git add and git commit to save changes. Use git branch feature to create the branch.

2

Make commits on both branches

Switch to the feature branch. Create a file named feature.txt with the content Feature work. Commit this change. Then switch back to main and create a file named main.txt with the content Main work. Commit this change.

Git

git init
echo "Initial commit" > README.md
git add README.md
git commit -m "Initial commit"
git branch feature
# Add commits on feature and main branches
# Your code here

Hint

Use git checkout feature to switch branches. Create and commit files on each branch separately.

3

Merge feature into main with a merge commit

Switch to the main branch. Use git merge feature to merge the feature branch into main creating a merge commit.

Git

git init
echo "Initial commit" > README.md
git add README.md
git commit -m "Initial commit"
git branch feature
git checkout feature
echo "Feature work" > feature.txt
git add feature.txt
git commit -m "Add feature work"
git checkout main
echo "Main work" > main.txt
git add main.txt
git commit -m "Add main work"
# Merge feature into main with a merge commit
# Your code here

Hint

Make sure you are on main branch before merging. Use git merge feature to combine branches with a merge commit.

4

Rebase feature onto main and fast-forward merge

Reset your repository to the state before the merge commit. Switch to feature branch. Use git rebase main to replay feature commits on top of main. Then switch to main and use git merge --ff-only feature to fast-forward merge feature into main.

Git

git init
echo "Initial commit" > README.md
git add README.md
git commit -m "Initial commit"
git branch feature
git checkout feature
echo "Feature work" > feature.txt
git add feature.txt
git commit -m "Add feature work"
git checkout main
echo "Main work" > main.txt
git add main.txt
git commit -m "Add main work"
git merge feature
# Reset to before merge, rebase feature on main, then fast-forward merge
# Your code here

Hint

Use git reset --hard HEAD~1 to undo the merge commit. Use git rebase main on feature. Then fast-forward merge with git merge --ff-only feature.

Practice

1. What does the --no-ff option do when merging branches in Git?

easy

A. It creates a merge commit even if a fast-forward merge is possible.

B. It squashes all commits into one before merging.

C. It deletes the source branch after merging.

D. It aborts the merge if conflicts are found.

Solution

1. Step 1: Understand fast-forward merges

   A fast-forward merge moves the branch pointer forward without creating a new commit if no divergent changes exist.

2. Step 2: Effect of --no-ff

   The --no-ff option forces Git to create a merge commit even if a fast-forward is possible, preserving branch history.

3. Final Answer:

   It creates a merge commit even if a fast-forward merge is possible. -> Option A

4. Quick Check:

   --no-ff keeps history with merge commit [OK]

Hint: Remember: --no-ff always makes a merge commit [OK]

Common Mistakes:

• Confusing --no-ff with --squash
• Thinking it deletes branches
• Assuming it aborts on conflicts

2. Which of the following is the correct syntax to perform a squash merge of branch feature into main?

easy

A. git merge --squash feature

B. git merge feature --no-ff

C. git merge --fast-forward feature

D. git merge --abort feature

Solution

1. Step 1: Identify squash merge syntax

   The --squash option is used with git merge to combine all commits from the source branch into one commit on the target branch.

2. Step 2: Check command correctness

   git merge --squash feature is the correct syntax to squash merge the feature branch into the current branch.

3. Final Answer:

   git merge --squash feature -> Option A

4. Quick Check:

   Squash merge syntax = git merge --squash [OK]

Hint: Use --squash right after git merge for squash merges [OK]

Common Mistakes:

• Placing --no-ff instead of --squash
• Using --abort which cancels merges
• Assuming --fast-forward is a valid option

3. Given the following commands run on branch main:

git merge feature

If feature has 3 commits and no conflicts, what will be the result in the commit history?

medium

A. A single new merge commit combining all changes from feature.

B. Merge aborted due to conflicts.

C. Three separate commits from feature added to main with no merge commit.

D. No new commits; main pointer moves forward (fast-forward).

Solution

1. Step 1: Understand default merge behavior

   By default, if the main branch has no new commits since branching, Git performs a fast-forward merge, moving the main pointer forward.

2. Step 2: Analyze the scenario

   Since feature has 3 commits and main has no new commits, Git will fast-forward main to feature's tip without creating a merge commit.

3. Final Answer:

   No new commits; main pointer moves forward (fast-forward). -> Option D

4. Quick Check:

   Default merge with no divergence = fast-forward [OK]

Hint: If no new commits on main, merge fast-forwards [OK]

Common Mistakes:

• Assuming a merge commit is always created
• Thinking commits are duplicated
• Confusing conflicts with no conflicts

4. You tried to merge branch feature into main using git merge feature, but Git reports conflicts. What is the best way to resolve this?

medium

A. Delete the feature branch and start over.

B. Run git merge --abort to cancel the merge and lose changes.

C. Manually edit conflicting files, then run git add and git commit.

D. Use git reset --hard to force merge.

Solution

1. Step 1: Understand merge conflicts

   Conflicts occur when Git cannot automatically combine changes. Manual intervention is needed to fix conflicting files.

2. Step 2: Resolve conflicts properly

   Edit the conflicting files to fix issues, then stage changes with git add and complete the merge with git commit.

3. Final Answer:

   Manually edit conflicting files, then run git add and git commit. -> Option C

4. Quick Check:

   Resolve conflicts manually, then add and commit [OK]

Hint: Fix conflicts manually, then add and commit [OK]

Common Mistakes:

• Aborting merge loses progress
• Deleting branches unnecessarily
• Using reset which discards changes

5. You want to merge a long-lived feature branch into main but keep the commit history clean with a single commit representing all changes. Which merge strategy should you use and what is the correct sequence?

hard

A. Use git merge --no-ff feature to keep all commits and a merge commit.

B. Use git merge --squash feature then commit manually.

C. Use git rebase main feature then fast-forward merge.

D. Delete feature and copy files manually.

Solution

1. Step 1: Identify goal - single commit for all changes

   Squash merge combines all commits from the feature branch into one commit on main, keeping history clean.

2. Step 2: Correct merge sequence

   Run git merge --squash feature to prepare changes, then create a new commit manually with git commit.

3. Final Answer:

   Use git merge --squash feature then commit manually. -> Option B

4. Quick Check:

   Squash merge + manual commit = single clean commit [OK]

Hint: Squash merge then commit for one clean commit [OK]

Common Mistakes:

• Using --no-ff which keeps all commits
• Confusing rebase with squash merge
• Deleting branches instead of merging