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 :
One-way function which is infeasible to invert
Small change in input yields large change in the output
Deterministic - same input yields same output
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:
