Repository (committed history) in Git - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of git log --oneline -3?

You run the command git log --oneline -3 in a repository with 5 commits. What will this command show?

Git

git log --oneline -3

A Shows the first 3 commits made in the repository with short hashes.

B Shows all 5 commits with full commit hashes and detailed commit messages.

C Shows the last 3 commits with their short commit hashes and commit messages.

D Shows only the commit messages of the last 3 commits without hashes.

💡 Hint

Think about what --oneline and -3 do in git log.

The --oneline option shows each commit in one line with a short hash and message. The -3 limits the output to the last 3 commits.

🧠 Conceptual

intermediate

What does the HEAD pointer represent in a Git repository?

In Git, what is the role of the HEAD pointer?

A <code>HEAD</code> points to the latest commit on the current branch you are working on.

B <code>HEAD</code> is the name of the remote repository.

C <code>HEAD</code> stores the list of all branches in the repository.

D <code>HEAD</code> is a backup of the repository before the last commit.

💡 Hint

Think about what Git uses to know your current working snapshot.

HEAD is a pointer that tells Git which commit your working directory is based on, usually the latest commit on your current branch.

❓ Troubleshoot

advanced

Why does git log --graph show a disconnected commit?

You run git log --graph and see a commit that is not connected to the main branch history. What could cause this?

Git

git log --graph

A The commit was deleted but still appears due to caching.

B The commit is corrupted and Git cannot link it properly.

C The repository is empty and has no commits.

D The commit belongs to a branch that was never merged into the main branch.

💡 Hint

Think about how branches and merges affect commit history graphs.

A commit that is not connected usually means it is on a branch that was never merged, so it does not appear in the main branch's history graph.

🔀 Workflow

advanced

What is the effect of git reset --hard HEAD~2?

What happens when you run git reset --hard HEAD~2 in your repository?

Git

git reset --hard HEAD~2

A Moves the current branch pointer back by 2 commits and resets the working directory and staging area to match that commit.

B Deletes the last 2 commits permanently from the remote repository.

C Creates a new branch named <code>HEAD~2</code>.

D Stashes the last 2 commits for later use.

💡 Hint

Consider what reset --hard does to the branch pointer and files.

git reset --hard HEAD~2 moves the current branch pointer back two commits and updates the working directory and index to match that commit, discarding changes after it.

✅ Best Practice

expert

Which Git command safely shows the commit history including merges with a clear visual graph?

You want to see the full commit history including merges, with a clear visual graph and branch names. Which command is best?

A git diff --graph

B git log --graph --oneline --all --decorate

C git show --graph

D git log --stat

💡 Hint

Look for options that show graph, all branches, and decorate with branch names.

git log --graph --oneline --all --decorate shows a visual graph of all commits including merges, with short commit info and branch names.

Practice

1. What does the git log command show in a Git repository?

easy

A. A list of all commits made in the repository history

B. The current status of files in the working directory

C. The list of branches in the repository

D. The remote repository URLs configured

Solution

1. Step 1: Understand the purpose of git log

   The git log command is designed to show the commit history of the repository, listing all saved changes.

2. Step 2: Differentiate from other commands

   Commands like git status show file changes, git branch shows branches, and git remote -v shows remote URLs, not commit history.

3. Final Answer:

   A list of all commits made in the repository history -> Option A

4. Quick Check:

   Commit history = git log output [OK]

Hint: Remember: git log = commit history list [OK]

Common Mistakes:

• Confusing git log with git status
• Thinking git log shows branches
• Mixing git log with remote info commands

2. Which of the following commands correctly shows a short, one-line summary of each commit in the history?

easy

A. git log --short

B. git log --oneline

C. git show --summary

D. git status --oneline

Solution

1. Step 1: Identify the correct flag for short commit view

   The --oneline option with git log shows each commit in a single line summary.

2. Step 2: Verify other options are incorrect

   git log --short is invalid, git show --summary shows details of one commit, and git status --oneline is invalid syntax.

3. Final Answer:

   git log --oneline -> Option B

4. Quick Check:

   Short commit list = git log --oneline [OK]

Hint: Use --oneline with git log for brief commit list [OK]

Common Mistakes:

• Using invalid flags like --short
• Confusing git show with git log
• Trying to use git status for commit history

3. Given this command output from git log --oneline:

f3a1b2c Fix typo in README
9d8e7f6 Add new feature X
4b3c2d1 Initial commit

What is the hash of the commit that added the new feature?

medium

A. 9d8e7f6

B. f3a1b2c

C. 4b3c2d1

D. Cannot tell from this output

Solution

1. Step 1: Read the commit messages and hashes

   The commit message "Add new feature X" corresponds to the hash 9d8e7f6.

2. Step 2: Match the message to the correct hash

   Each line shows the hash first, then the message. So the hash for adding the feature is 9d8e7f6.

3. Final Answer:

   9d8e7f6 -> Option A

4. Quick Check:

   Commit message matches hash 9d8e7f6 [OK]

Hint: First word is hash, rest is message in git log --oneline [OK]

Common Mistakes:

• Picking the wrong hash for the message
• Thinking hashes are at the end
• Assuming output is incomplete

4. You ran git log --oneline but got an error: error: unknown option `--oneline'. What is the most likely cause?

medium

A. You typed the command in the wrong folder

B. You must run git fetch before using --oneline

C. You need to add git log --oneline --all to fix it

D. Your Git version is too old and does not support --oneline

Solution

1. Step 1: Understand the error message

   The error says the option --oneline is unknown, meaning Git does not recognize it.

2. Step 2: Identify the cause

   This usually happens if the Git version is old and does not support the --oneline flag.

3. Final Answer:

   Your Git version is too old and does not support --oneline -> Option D

4. Quick Check:

   Unknown option error = outdated Git version [OK]

Hint: Unknown option often means Git version is outdated [OK]

Common Mistakes:

• Assuming wrong folder causes option error
• Thinking fetch fixes option errors
• Adding unrelated flags to fix syntax

5. You want to see a quick summary of the last 3 commits in your repository, each on one line. Which command should you use?

hard

A. git log --oneline --last 3

B. git log --3 --oneline

C. git log --oneline -n 3

D. git log --limit=3 --oneline

Solution

1. Step 1: Identify the correct option to limit commits

   The -n 3 or --max-count=3 option limits the number of commits shown.

2. Step 2: Combine with --oneline for short output

   Using git log --oneline -n 3 shows the last 3 commits in one-line format.

3. Step 3: Check other options for correctness

   --3 is invalid, --last 3 and --limit=3 are not valid git log options.

4. Final Answer:

   git log --oneline -n 3 -> Option C

5. Quick Check:

   Limit commits with -n, short view with --oneline [OK]

Hint: Use -n with --oneline to limit commits shown [OK]

Common Mistakes:

• Using invalid flags like --last or --limit
• Trying --3 which is invalid
• Mixing order of options incorrectly