SHA-1 hashing concept in Git - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to show the SHA-1 hash of a file named example.txt.

Git

git hash-object [1]

Drag options to blanks, or click blank then click option'

Aexample.txt

Bcommit

Cinit

Dstatus

Attempts:

3 left

💡 Hint

Common Mistakes

Using git commands unrelated to hashing like 'commit' or 'status'.

Forgetting to specify the file name.

The command git hash-object example.txt calculates the SHA-1 hash of the file example.txt.

2fill in blank

medium

Complete the command to create a new Git object from the file data.txt and print its SHA-1 hash.

Git

git hash-object -[1] data.txt

Drag options to blanks, or click blank then click option'

Ac

Br

Cw

Dm

Attempts:

3 left

💡 Hint

Common Mistakes

Using -r which is not a valid option here.

Using -c or -m which are unrelated.

The -w option writes the object into the Git database and prints its SHA-1 hash.

3fill in blank

hard

Fix the error in the command to get the SHA-1 hash of file.txt by filling the blank.

Git

git hash-object [1] file.txt

Drag options to blanks, or click blank then click option'

A-r

B-w

C--hash

D--stdin

Attempts:

3 left

💡 Hint

Common Mistakes

Using -r which is invalid here.

Using --stdin which expects input from standard input.

The correct option to write the object and get its SHA-1 hash is -w. The others cause errors or do not produce the hash.

4fill in blank

hard

Fill both blanks to create a SHA-1 hash of README.md and store it in the Git database.

Git

git hash-object [1] [2]

Drag options to blanks, or click blank then click option'

A-w

BREADME.md

C-r

Dfile.txt

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong file names like file.txt.

Using -r instead of -w.

The -w option writes the object, and README.md is the file to hash.

5fill in blank

hard

Fill all three blanks to create a SHA-1 hash of script.sh, write it to the Git database, and then display the hash.

Git

hash=$([1] [2] [3]) && echo $hash

Drag options to blanks, or click blank then click option'

Agit hash-object

B-w

Cscript.sh

D-r

Attempts:

3 left

💡 Hint

Common Mistakes

Using -r instead of -w.

Forgetting to specify the file name.

The command hash=$(git hash-object -w script.sh) writes the object and returns the SHA-1 hash, which is stored in hash and then printed.

Practice

1. What does the SHA-1 hash in Git uniquely identify?

easy

A. A specific commit or file content

B. The username of the committer

C. The branch name

D. The date and time of the commit

Solution

1. Step 1: Understand SHA-1 purpose in Git

   SHA-1 generates a unique code based on the content of files or commits.

2. Step 2: Identify what SHA-1 represents

   It uniquely identifies the exact content or commit, not metadata like username or branch.

3. Final Answer:

   A specific commit or file content -> Option A

4. Quick Check:

   SHA-1 = unique content ID [OK]

Hint: SHA-1 hashes content, not user or branch info [OK]

Common Mistakes:

• Thinking SHA-1 identifies user info
• Confusing SHA-1 with branch names
• Assuming SHA-1 stores commit date

2. Which command correctly shows the SHA-1 hash of the latest commit in a Git repository?

easy

A. git log -1 --format=%H

B. git sha1sum HEAD

C. git show --hash

D. git commit --hash

Solution

1. Step 1: Recall Git command to show commit hash

   The command 'git log -1 --format=%H' prints the full SHA-1 hash of the latest commit.

2. Step 2: Check other options for correctness

   The other options are invalid or do not exist in Git syntax.

3. Final Answer:

   git log -1 --format=%H -> Option A

4. Quick Check:

   Correct Git syntax for latest commit SHA-1 is git log -1 --format=%H [OK]

Hint: Use git log with format %H for full commit hash [OK]

Common Mistakes:

• Using non-existent git commands
• Confusing commit message commands with hash commands
• Trying to use sha1sum directly on HEAD

3. Given the command git hash-object README.md, what is the expected output?

medium

A. An error because README.md is not a commit

B. The size of README.md in bytes

C. The last commit hash that modified README.md

D. The SHA-1 hash of the README.md file content

Solution

1. Step 1: Understand git hash-object command

   This command computes and outputs the SHA-1 hash of the file content given (README.md here).

2. Step 2: Verify output meaning

   It does not show file size, commit hashes, or errors for valid files.

3. Final Answer:

   The SHA-1 hash of the README.md file content -> Option D

4. Quick Check:

   git hash-object outputs file content SHA-1 [OK]

Hint: git hash-object hashes file content, not commits [OK]

Common Mistakes:

• Expecting commit hash instead of file hash
• Thinking it outputs file size
• Assuming it errors on normal files

4. You run git hash-object -w file.txt but get an error. What is the most likely cause?

medium

A. The -w option is not valid for git hash-object

B. The file.txt does not exist in the current directory

C. You need to commit before hashing

D. The file.txt is already tracked by Git

Solution

1. Step 1: Understand git hash-object -w usage

   The -w option writes the object to Git's object database; it requires the file to exist.

2. Step 2: Identify cause of error

   If file.txt does not exist, the command errors. Other options are incorrect because -w is valid, committing is not required, and tracking status doesn't cause this error.

3. Final Answer:

   The file.txt does not exist in the current directory -> Option B

4. Quick Check:

   Missing file causes git hash-object -w error [OK]

Hint: Check file existence before git hash-object -w [OK]

Common Mistakes:

• Thinking -w is invalid option
• Assuming commit is required before hashing
• Believing tracked files cause this error

5. You want to verify if a file's content matches a specific Git object SHA-1 hash. Which sequence of commands correctly helps you do this?

hard

A. Run git show SHA1_HASH and compare with file.txt content manually

B. Run git diff SHA1_HASH file.txt to see differences

C. Run git hash-object file.txt and compare output with the SHA-1 hash

D. Run git cat-file -p file.txt to get the hash

Solution

1. Step 1: Understand how to get file's SHA-1 hash

   Use 'git hash-object file.txt' to compute the SHA-1 hash of the file content.

2. Step 2: Compare computed hash with given SHA-1

   If the hashes match, the file content matches the Git object.

3. Final Answer:

   Run git hash-object file.txt and compare output with the SHA-1 hash -> Option C

4. Quick Check:

   Compare file hash with SHA-1 using git hash-object [OK]

Hint: Use git hash-object to get file hash for comparison [OK]

Common Mistakes:

• Using git show to compare file content directly
• Trying git diff with SHA-1 hash and file
• Using git cat-file incorrectly on files