git merge command - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of a fast-forward merge

You have a branch feature that is ahead of main with new commits. You run git checkout main and then git merge feature. What is the output?

Git

git checkout main
git merge feature

A

Updating abc1234..def5678
Fast-forward

B

Auto-merging file.txt
CONFLICT (content): Merge conflict in file.txt

C Already up to date.

D error: You have unmerged files.

💡 Hint

Think about what happens when the target branch has no new commits since the source branch diverged.

When the target branch has no new commits and the source branch is ahead, git performs a fast-forward merge, updating the target branch pointer to the source branch commit. The output shows the commit range and 'Fast-forward'.

💻 Command Output

intermediate

Result of merging with conflicts

You try to merge branch feature into main, but both branches changed the same lines in a file. What output does git merge feature produce?

Git

git checkout main
git merge feature

A

Auto-merging file.txt
CONFLICT (content): Merge conflict in file.txt
Automatic merge failed; fix conflicts and then commit the result.

B Already up to date.

C error: Your local changes to the following files would be overwritten by merge

D Fast-forward

💡 Hint

Conflicts happen when the same lines are changed differently in both branches.

Git reports the conflicting file and shows a conflict message. It stops the merge and asks you to fix conflicts manually before committing.

❓ Configuration

advanced

Configuring merge strategy for a branch

You want to always use the 'ours' merge strategy when merging the experimental branch into main. Which git config command sets this behavior?

A git config branch.main.merge '--strategy=ours'

B git config branch.experimental.mergeoptions '--strategy=ours'

C git config branch.experimental.merge '--strategy=ours'

D git config branch.main.mergeoptions '--strategy=ours'

💡 Hint

The config key for merge options is under the branch name you want to configure.

The mergeoptions config is set per branch and applies when merging into that branch. To always use 'ours' strategy when merging experimental into main, set it under branch.main.mergeoptions.

❓ Troubleshoot

advanced

Cause of 'fatal: refusing to merge unrelated histories' error

You run git merge feature but get the error fatal: refusing to merge unrelated histories. What is the most likely cause?

A There are uncommitted changes in the working directory.

B The branches come from repositories with no common commit history.

C The feature branch has merge conflicts.

D The main branch is already up to date.

💡 Hint

Think about what it means for histories to be unrelated.

This error happens when git tries to merge two branches that do not share any common ancestor commit, often because they come from different repositories initialized separately.

🔀 Workflow

expert

Correct sequence to merge a remote branch with conflict resolution

You want to merge the remote branch origin/feature into your local main branch and resolve conflicts if any. What is the correct order of commands?

A 1,3,2,4

B 1,2,3,4

C 2,1,3,4

D 2,3,1,4

💡 Hint

You must update your remote tracking branches before merging.

First fetch updates remote branches, then checkout main, merge the remote feature branch, and finally resolve conflicts if any before committing.

Practice

1. What does the git merge command do in Git?

easy

A. It combines changes from one branch into the current branch.

B. It deletes a branch permanently.

C. It creates a new branch from the current branch.

D. It shows the commit history of the current branch.

Solution

1. Step 1: Understand the purpose of git merge

   The git merge command is used to combine changes from one branch into another branch.

2. Step 2: Identify the correct description

   Among the options, only It combines changes from one branch into the current branch. correctly describes merging changes into the current branch.

3. Final Answer:

   It combines changes from one branch into the current branch. -> Option A

4. Quick Check:

   git merge = combine branches [OK]

Hint: Merge means combine changes into current branch [OK]

Common Mistakes:

• Confusing merge with branch deletion
• Thinking merge creates a new branch
• Mixing merge with viewing history

2. Which of the following is the correct syntax to merge branch feature into the current branch?

easy

A. git merge --create feature

B. git merge -b feature

C. git merge feature

D. git merge --delete feature

Solution

1. Step 1: Recall the basic merge syntax

   The correct syntax to merge a branch is git merge branch_name.

2. Step 2: Match the syntax with options

   git merge feature matches the correct syntax. Options B, C, and D use invalid flags or commands.

3. Final Answer:

   git merge feature -> Option C

4. Quick Check:

   git merge + branch name = correct syntax [OK]

Hint: Use 'git merge branch_name' to merge branches [OK]

Common Mistakes:

• Adding incorrect flags like -b or --create
• Confusing merge with branch creation or deletion
• Using merge without specifying branch name

3. Given the following commands run in order:

git checkout main
git merge feature

What happens if the feature branch has commits not in main?

medium

A. The main branch is reset to feature branch state.

B. The feature branch is deleted automatically.

C. Git throws an error and stops the merge.

D. The commits from feature are added to main.

Solution

1. Step 1: Understand merge behavior with new commits

   When merging a branch with new commits, Git combines those commits into the current branch.

2. Step 2: Analyze the options

   The commits from feature are added to main correctly describes this behavior. Options B, C, and D describe incorrect or unrelated behaviors.

3. Final Answer:

   The commits from feature are added to main. -> Option D

4. Quick Check:

   Merge adds commits [OK]

Hint: Merge adds commits, does not delete branches [OK]

Common Mistakes:

• Thinking merge deletes branches
• Expecting merge to reset branches
• Assuming merge always fails with new commits

4. You run git merge feature but Git reports a conflict. What should you do next?

medium

A. Restart Git to clear the conflict.

B. Manually resolve the conflicts in files, then run git add and git commit.

C. Run git merge --force to ignore conflicts.

D. Delete the feature branch and try merging again.

Solution

1. Step 1: Understand merge conflicts

   When Git reports conflicts, it means changes clash and need manual fixing.

2. Step 2: Resolve conflicts properly

   You must edit conflicted files to fix issues, then stage and commit the changes to complete the merge.

3. Final Answer:

   Manually resolve the conflicts in files, then run git add and git commit. -> Option B

4. Quick Check:

   Fix conflicts manually, then add and commit [OK]

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

Common Mistakes:

• Trying to force merge ignoring conflicts
• Deleting branches to fix conflicts
• Restarting Git expecting conflicts to clear

5. You want to merge branch feature into main but keep main's changes in case of conflict (favor main). Which command helps achieve this?

hard

A. git merge -X ours feature

B. git merge --no-ff feature

C. git merge -s recursive feature

D. git merge --abort feature

Solution

1. Step 1: Understand merge strategies

   The -X ours option tells Git to favor the current branch's changes during conflicts.

2. Step 2: Match the option to the goal

   git merge -X ours feature uses -X ours to keep main's changes if conflicts occur. Other options do not achieve this.

3. Final Answer:

   git merge -X ours feature -> Option A

4. Quick Check:

   Use -X ours to favor current branch on conflicts [OK]

Hint: Use 'git merge -X ours' to keep current branch changes [OK]

Common Mistakes:

• Confusing -X ours with --no-ff
• Using --abort to fix conflicts
• Not specifying strategy option