1. Distributed version control with git
— a brief introduction
Joel Krebs
Slides by Oscar Nierstrasz

2. Why git?

3. Bob

4. Bob
Carol

5. Bob
Carol
Alice
Ted

6. Bob
Carol
Alice
Ted
A recipe for disaster!

7. What is git?

8. > Distributed revision control system
> Originally developed by Linus Torvalds for the
development of the Linux Kernel in 2005
> Focus on speed and efficiency
> Quite a unique design and therefore sometimes a bit
scary and difficult to understand

9. The git object model

10. A “blob” is content under
version control (a file)
blob

11. You can have trees of blobs
(directories of files)
tree
blob
tree
blob
blob

12. A “commit” is a tree of blobs
(a set of changes)
commit
tree
blob
tree
blob
blob

13. Most commits modify
(or merge) earlier
commits
commit
commit
tree
tree
blob
blob
tree
blob
blob

14. You can “tag” an
interesting commit
tag
commit
commit
tree
tree
blob
blob
tree
blob
blob

15. A graph of commits
may belong to a branch branch
tag
commit
commit
tree
tree
blob
blob
tree
blob
blob

16. HEAD
“HEAD “is the
current branch
branch
tag
commit
commit
tree
tree
blob
blob
tree
blob
blob

17. HEAD
branch
commit
commit
Let’s focus on commits
and branches

18. Basic git

19. Create a git repo
HEAD
master
C0

20. Tell git to “stage”
changes
HEAD
master
C0

21. HEAD
master Commit your
changes
C1
C0

22. Collaborating

23. John Jane
Local repo Public repo Local repo
master
C1
C0

24. John Jane
Local repo Public repo Local repo
master master master
C1 C1 C1
C0 C0 C0

25. John Jane
Local repo Public repo Local repo
master master master
C2 C1 C3
C1 C0 C1
C0 C0

26. John Jane
Local repo Public repo Local repo
master master master
C2 C1 C3
C1 C0 C1
C0 C0
(nothing new to pull)

27. John Jane
Local repo Public repo Local repo
master master master
C2 C2 C3
C1 C1 C1
C0 C0 C0

28. John Jane
Local repo Public repo Local repo
master master master
C2 C2 C3 C2
C1 C1 C1
C0 C0 C0

29. John Jane
Local repo Public repo Local repo
master master master
C2 C2 C4
C1 C1 C3 C2
C0 C0 C1
C0
NB: git pull = fetch + merge

30. John Jane
Local repo Public repo Local repo
master master master
C2 C4 C4
C1 C3 C2 C3 C2
C0 C1 C1
C0 C0

31. John Jane
Local repo Public repo Local repo
master master master
C4 C4 C4
C3 C2 C3 C2 C3 C2
C1 C1 C1
C0 C0 C0

32. Branching
and merging

33. “origin” refers to the
remote repo
HEAD
master
origin/master
C1
C0

34. HEAD
master
origin/master C2
C1
C0

35. HEAD
tryout
master
origin/master C2
C1
C0

36. HEAD
tryout
master
origin/master C2
C1 NB: git checkout –b … =
branch + checkout
C0

37. HEAD
tryout
master
C3
origin/master C2
C1
C0

38. HEAD
tryout
master
C3 C5
C2
origin/master
C1 C4 C6
C0 origin/idea

39. HEAD
tryout
C7
master
C3 C5
C2
origin/master
C1 C4 C6
C0 origin/idea

40. tryout
HEAD
C7
master
C3 C5
C2
origin/master
C1 C4 C6
C0 origin/idea

41. HEAD
tryout
master
C7
C8
C3 C5
C2
origin/master
C1 C4 C6
C0 origin/idea

42. HEAD
tryout
master
C7
origin/master C8
C3 C5
C2
C1 C4 C6
C0 origin/idea

43. Overview git workflow
Remote repository
fetch push
Local repository
pull commit
checkout Index (cache)
HEAD add
Working directory

44. Getting started

45. First steps
> Follow instructions on P2 Blog for installation
> Send your ssh public key to joel.krebs@students.unibe.ch
> Create meaningful commits with according messages
> Hints that make your life easier:
—Create a .gitignore file
—Always pull before you push
—Don’t panic when merge conflicts occur

46. More to git

47. More to git …
> Merging and mergetool
> Squashing commits when merging
> Resolving conflicts
> User authentication with ssh
> gitx and other graphical tools
> git configure — remembering your name
> git remote — multiple remote repos
> github — an open source public repo
> …

48. Resources
http://git-scm.com/ http://book.git-scm.com/index.html
http://gitready.com/
https://github.com/
http://www.slideshare.net/chacon/getting-git http://oreilly.com/

49. http://creativecommons.org/licenses/by-sa/3.0/