SHA-1 hashing concept in Git - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is SHA-1 in the context of Git?

SHA-1 is a cryptographic hash function that Git uses to uniquely identify commits, files, and other objects by generating a 40-character hexadecimal string.

beginner

Why does Git use SHA-1 hashes for its objects?

Git uses SHA-1 hashes to ensure data integrity and to quickly check if content has changed by comparing unique hash values instead of the full content.

beginner

How long is a SHA-1 hash string in Git?

A SHA-1 hash string in Git is 40 characters long, consisting of hexadecimal digits (0-9 and a-f).

intermediate

What happens if two different files produce the same SHA-1 hash in Git?

This is called a collision and is extremely rare. Git relies on SHA-1's uniqueness to avoid collisions, ensuring each object is uniquely identified.

beginner

How can you see the SHA-1 hash of the latest commit in a Git repository?

You can run the command git log -1 --format=%H to display the full SHA-1 hash of the latest commit.

What does a SHA-1 hash represent in Git?

A A unique identifier for Git objects

B The size of a file in bytes

C The date and time of a commit

D The username of the committer

SHA-1 hashes uniquely identify Git objects like commits and files.

How many characters long is a SHA-1 hash string in Git?

A 64 characters

B 20 characters

C 40 characters

D 128 characters

SHA-1 hashes are 40 hexadecimal characters long.

Which Git command shows the SHA-1 hash of the latest commit?

A git show HEAD

B git log -1 --format=%H

C git status

D git diff

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

Why is SHA-1 hashing important in Git?

A To compress files

B To speed up network transfers

C To encrypt commit messages

D To uniquely identify and verify data integrity

SHA-1 hashes help Git uniquely identify objects and verify their integrity.

What is a collision in SHA-1 hashing?

A When two different inputs produce the same hash

B When a hash is too long

C When a commit is lost

D When a file is deleted

A collision happens if two different inputs generate the same SHA-1 hash, which is very rare.

Explain what SHA-1 hashing is and why Git uses it.

Think about how Git tracks changes and verifies data.

Describe how you can find the SHA-1 hash of a commit in Git and what it represents.

Focus on commands and the purpose of the hash.