How GitWorks Git IsNotWhatYouThink Were going to talk aboutthe - PowerPoint PPT Presentation

How GitWorks Git IsNotWhatYouThink

We’re going to talk aboutthe internals ofGit.

“Porcelain” Commands gitadd ▪ gitcommit ▪ git push ▪ gitpull ▪ git branch ▪ gitcheckout ▪ git merge ▪ gitrebase ▪ … ▪

“Plumbing” Commands git cat-file ▪ git hash-object ▪ gitcount-objects ▪ … ▪

If youwant to masterGit, don’t worry about learning thecommands. Instead, learn themodel.

Git

GitIs.. …a Distributed RevisionControl System

GitIs.. …a Revision ControlSystem

GitIs.. …a Stupid Content Tracker

GitIs.. …a PersistentMap

Values andKeys Any sequence ofbytes SHA1hash

Values andKeys “ApplePie” 23991897e13e47ed0adb91a0082c31c82fe0cbe5

Every object in Git hasitsown SHA1. So, what if theycollide?

Winning theJackpot 1 chance in175.000.000

Winning theJackpot

Chances of Two SHA1sColliding

SHA1s are unique in theuniverse.

GitIs.. …a PersistentMap

GitIs.. …a Stupid Content Tracker

The ObjectDatabase ./ 1177 be4d

The ObjectDatabase 3ee7 recipes/ ./ menu.txt 1177 be4d Apple Pie 2399

The ObjectDatabase Put your recipes in this directory, one README.txt recipe per file. 3ee7 361a recipes/ apple_pie.txt ./ menu.txt 1177 be4d Apple Pie 2399

The Git ObjectModel Put your recipes in this directory, one README.txt recipe per file. 3ee7 361a recipes/ apple_pie.txt ./ menu.txt 1177 be4d Apple Pie 2399

The Git ObjectModel Put your recipes in this directory, one README.txt recipe per file. 3ee7 361a 2508 recipes/ apple_pie.txt ./ menu.txt 1177 be4d Apple Pie 2399

The Git ObjectModel Put your recipes in this directory, one README.txt recipe per file. ./ 3ee7 361a 2508 6ee0 recipes/ apple_pie.txt ./ menu.txt 1177 be4d Apple Pie 2399

The Git ObjectModel Apple Pie Cheesecake f1fe menu.txt Put your recipes in this directory, one README.txt recipe per file. ./ recipes/ 3ee7 361a 2508 6ee0 recipes/ apple_pie.txt ./ menu.txt 1177 be4d Apple Pie 2399

The Git ObjectModel Apple Pie Cheesecake mytag f1fe menu.txt Put your recipes in this directory, one README.txt recipe per file. ./ recipes/ 3ee7 361a 2508 6ee0 recipes/ apple_pie.txt ./ menu.txt 1177 be4d Apple Pie 2399

GitObjects Blobs ▪ Trees ▪ Commits ▪ AnnotatedTags ▪

What Git ReallyIs f1fe 3ee7 361a 2508 6ee0 1177 be4d 2399

GitIs.. …a Stupid Content Tracker