Behind the scenes of GIT

what is .git folder ?

it is folder which git create when we initialize any project to track by th command `git init`. git use this folder to store all the commits, tags, blobs, tree , heads, branch any many other things to keep track our changes in files.

what is inside .git/ ?

there are files and directory like

• HEAD

• refs/

• objects/

• hooks/

• info/

• logs/

• index

• config

1.Config

 it is file for customization of repo like color, alias , remote etc.

```
# color customization
[user]
  name=some name
  email=some email
[color]
  ui=true
[color "branch"]
  local= cyan bold
  current= magenta
[color "diff"]
  old=add some color
  new=add another color

```

2.refs/

it is directory that store pointer of heads , tags, remotes .. etc.inside heads/ there are reference for latest commit-hash for branch like master, bugFix, darkMode, many other branches.

3.objcts/

The objects directory contains all the repo files. This is where Git stores the backups of files, the commits in a repo, and more. The files are all compressed and encrypted, so they won't look like much

4-types of GIT objects

- commit
- blobs
- tree
- annotated tags

Hashing Function

the function which map the inputs of arbitrary size into some fixed size output.

Cryptographic Hashing :

1. One-way function which is infeasible to invert

2. Small change in input yields large change in the output

3. Deterministic - same input yields same output

4. Unlikely to find 2 outputs with same value

Note: git use SHA-1 algorithm for hashing function which gives 40 characters hexadecimal number which is commit-hash, blobs-hash etc.

Git Database

Git is a key-value data store. We can insert any kind of content into a Git repository, and Git will hand us back a unique key we can later use to retrieve that content. These keys that we get back are SHA-1 checksums.

blobs:

Git blobs (binary large object) are the object type Git uses to store the contents of files in a given repository. Blobs don't even include the filenames of each file or any other data. They just store the contents of a file.

Trees:

Trees are Git objects used to store the contents of a directory. Each tree contains pointers that can refer to blobs and to other trees. Each entry in a tree contains the SHA-1 hash of a blob or tree, as well as the mode, type, and filename.

Some Commands:

• viewing trees : git cat-file -p master^{tree}

• git cat-file -t <object-hash> : tell about type of object like commit, blob, tree

Commits:

Commit objects combine a tree object along with information about the context that led to the current tree. Commits store a reference to parent commit(s), the author, the committer, and of course the commit message!.

• every commit got reference to previous commit in parent:<commit-hash>

• we can see by using `git cat-file -p <commit-hash>`

Some Terms :

• tree : structure of project while committing the project .

• blob : content store in file is blob.

• author:

• committer:

• message

NOTE : everything is stored as hashed in objects directory so that git can retrieve data by the hashed key which is output of SHA-1 hashing function

Resources:

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