Git

Question 1

What is delta storage model of source code control?

Answer 1

First commit stores all the files, and the later commits stores the diffs from the original version and subsequent versions

Question 2

What is DAG storage model of source code control?

Answer 2

It stores the snapshot of each file with each commit

Question 3

What is the advantage of delta storage?

Answer 3

It is space efficient

Question 4

How does the source code control taxonomy look like?

Answer 4

Question 5

How to override the .git directory?

Answer 5

By using the GIT_DIR environment variable

Question 6

What are the basic contents of git directory?

Answer 6

config file, hooks, index, object database, references

Question 7

How is new content stored in the object database

Answer 7

type + ‘ ‘ + content.size + ‘\0’ + content

Question 8

Which hash algorithm is used by git?

Answer 8

SHA1

Question 9

How is content stored on the disk?

Answer 9

It is stored in a compressed format with the file name being the first few letters of the hash

Question 10

What does git gc achieve?

Answer 10

It finds all the objects that point to the same file with minor differences, packs the changes in a .pack file and also creates a .idx file that points to different places in the .pack file. It also deletes the compressed objects after this activity

Question 11

What is “loose format” vs “packed format”?

Answer 11

Objects stored in compressed form in directories are loose format, while objects stored in .pack file is packed format

Question 12

What are 4 types of git objects?

Answer 12

blob, tree, commit, tag

Question 13

What is a blob?

Answer 13

Every file is converted to a blob in the .git directory

Question 14

How is a file converted to blob?

Answer 14

Take the file, add the header, calculate the checksum, compress and store the file

Question 15

What is a tree object?

Answer 15

Every directory is a tree object

Question 16

How is a tree object made?

Answer 16

A directory listing is made with each entry containing the mode of the file, type of the entry, checksum and the file name. Then it is compressed and stored as a tree object

Question 17

What does a commit object consist of?

Answer 17

A commit message, the author and email, a parent commit which is the commit before this commit and a tree pointer which is basically directory listing at the time of this commit message

Question 18

What is a tag object?

Answer 18

A pointer to the commit object, along with the tag name, author and a tag message

Question 19

What is a reference?

Answer 19

Its a movable pointers to commits

Question 20

Where are refs stored?

Answer 20

in .git/refs/* as simple files

Question 21

What does HEAD point to? What does tag, branch or remote point to?

Answer 21

a branch. Rest all point to a commit

Question 22

What happens when a file is changed and committed?

Answer 22

The blob for the corresponding file changes, and the tree that points to the blob changes and this change propagates up the hierachy until a new commit object is made that points to the new tree object, then the branch points to the new commit object and so does the HEAD

Question 23

What happens when we do a git checkout -b

Answer 23

HEAD points to a new branch which points to the current commit. The master pointer is not changed

Question 24

How does the history look like between git merge and git rebase

Answer 24

git rebase history looks like linear (one started where other left off) where as git merge history looks like parallel (both worked at the same time)

Question 25

What does master@{yesterday} mean?

Answer 25

where master is at, yesterday

Question 26

what does master@{5} mean?

Answer 26

5th prior value of master

Question 27

What does master^2 mean?

Answer 27

2nd parent of master (in case of multi-way merge)

Question 28

What does master~2 mean?

Answer 28

2nd grandparent of master

Question 29

What does master:/path/to/file give

Answer 29

It give the blob spec of that file in master

Question 30

What does v1.0:/path/to/file give?

Answer 30

Blob of the file in the tag v1.0

Question 31

What does … give? and .. give?

Answer 31

The former gives everything between two commits and the latter gives everything since that commit

Question 32

What does index file in .git track?

Answer 32

A simple file that tracks what is staged, what is modified and what is present in the git directory

Question 33

What are different git protocols to clone?

Answer 33

ssh, http[s], file:///, git://, rsync://

Question 34

How to make git log show the commits in different ways?

Answer 34

git log –pretty=oneline

git log –pretty=format

Question 35

What does fetch + merge otherwise called as?

Answer 35

pull