Git, Git Internals

1. Git

2. Literally,

3. /ɡɪt/
Noun INFORMAL • BRITISH
1. an unpleasant or contemptible person.

4. “I’m an egotistical bastard, and I name all my
projects after myself. First Linux, now git.”
- Linus Torvalds -

5. History

6. Understanding Git

8. Git != Subversion + Magic

9. What is Git ?

10. Git : A Stupid Content Tracker

11. “ In many ways you can just see git as a filesystem — it’s
content addressable, and it has a notion of versioning,
but I really really designed it coming at the problem from
the viewpoint of a filesystem person (hey, kernels is
what I do), and I actually have absolutely zero
interest in creating a traditional SCM system.”
- Linus -

12. Focus and Design

13. Non Linear Development
Branching and Merging

14. Distributed Development
No repository is special or central in git - each clone is basically equal.

15. Efficiency

16. The Ruby on Rails Git repository download, which
includes the full history of the project – every version
of every file, weighs in at around 13M, which is not
even twice the size of a single checkout of the project
(~9M). The Subversion server repository for the
same project is about 115M.

17. Git Object Types

18. Working Directory (Example)

19. Blob (Immutable)

20. Tree (Imutable)

21. Commit (Immutable)

22. The current record for number of commit parents in the
Linux kernel is 12 branches merged in a single commit!

23. Tag (Immutable)

24. Git Data Model
Mutable
Immutable

25. Git Data Model
Mutable
Immutable

26. Git Data Model (first commit)
base_include.rb
base directory
lib directory
my_plugin.rb
init.rb
master (default)
Mutable
Immutable
Reference :

27. Git Data Model (second commit)
● modify the lib/base/base_include.rb file
● commit
● tag this commit

28. Git Data Model (second commit)
base_include.rb #v1
base directory
lib directory
1st
commit 2nd
commit
lib directory
base directory
base_include.rb #v2
init.rb
my_plugin.rb
Mutable
Immutable
Reference :
master (default)

29. Git Data Model (third commit)
● modify the init.rb file
● commit

30. Git Data Model (third commit)
base_include.rb #v1
base Directory
lib Directory
1st
Commit
2nd
Commit
Init.rb #v1
my_plugin.rb
base_include.rb #v2
base Directory
lib Directory
3rd
Commit
init.rb #v2
master(default)
Mutable
Immutable
Reference :

31. Git Data Model (third commit)
So, to keep all the information and history on the three
versions of this tree, Git stores 16 immutable, signed,
compressed objects.

32. Branching and Merging
Creating a branch is nothing more than just writing 40
characters to a file in .git/refs/heads directory.

33. Merging

34. Merging

35. Rebasing v Merging
Merging Rebasing

36. Main Sections of Git Project

38. Infact, all of the contents of this slide are taken from Git Internals by Scott Chacon 😛
References
1. Git Internals ( Scott Chacon )
2. Pro Git ( Scott Chacon and Ben Straub)
3. Git and Github Social Coding Advanced Javazone (Talk by Tim Berglund
@tlberglund )
4. Advanced Git for developers Laracon EU 2015 ( Talk by Lorna Jane Mitchell )