Git: From init to a KV Database

#FF0000 Leather Pants.

Developer.

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Git

An Introduction

mkdir git_stuff
cd git_stuff
git init

tree .git

.git
├── branches
├── config
├── description
├── HEAD
├── hooks
│   ├── applypatch-msg.sample
│   ├── commit-msg.sample
│   ├── post-update.sample
│   ├── pre-applypatch.sample
│   ├── pre-commit.sample
│   ├── prepare-commit-msg.sample
│   ├── pre-push.sample
│   ├── pre-rebase.sample
│   └── update.sample
├── info
│   └── exclude
├── objects
│   ├── info
│   └── pack
└── refs
    ├── heads
    └── tags

Directed Acyclic Graph vs Tree

Objects

Hashin' and Cattin'

echo "test" > test.txt

git status

git add test.txt
git commit -m 'YOLO'

tree .git
.git
├── branches
├── COMMIT_EDITMSG
├── config
├── description
├── HEAD
├── hooks
│   ├── ...
│   └── update.sample
├── index
├── info
│   └── exclude
├── logs
│   ├── HEAD
│   └── refs
│       └── heads
│           └── master
├── objects
│   ├── 2b
│   │   └── 297e643c551e76cfa1f93810c50811382f9117
│   ├── 8c
│   │   └── dd94550187df2f165cc67305fe9fcc27b98e62
│   ├── 9d
│   │   └── aeafb9864cf43055ae93beb0afd6c7d144bfa4
│   ├── info
│   └── pack
└── refs
    ├── heads
    │   └── master
    └── tags

15 directories, 21 files

│   ├── 9d
│   │   └── aeafb9864cf43055ae93beb0afd6c7d144bfa4

Naming Format:

2 chars as dirname + hash inside

echo "Yolt" | git hash-object -w --stdin
#=> 8ac7f99313f02f7bfaf45426ffe514075232bad4

# -w = actually write data
# --stdin to take the i/o from stdin

git cat-file -p 8ac7f99313f02f7bfaf45426ffe514075232bad4

#=> Yolt

hash-object == set

cat-file == get

A Bit Deeper

Every Version. Ever

.git/objects/two_chars/rest_of_hash

Wrapping it as a DB

Ruby time!