Whether you work alone or in a team, some sort of source control management is essential to you as a developer for things like keeping a history of your code, dealing with integrating code, managing releases and making your development workflow through different features painless. If you're coming from something like CVS or SVN, the open-source Git version control system will turn what you know of SCM on its head. In this presentation from AnDevCon 2011, EffectiveUI’s Tony Hillerson explains why Git is different, and what that difference means to you as an Android developer.

1. Git
For the Android Developer
AnDevCon 2011 : Tony Hillerson
#AnDevCon #effectiveui
http://www.slideshare.net/thillerson/scm-for-android-developers-using-git

2. About Me
• Worked with Android and Git for a few years now
• O’Reilly Screencaster: Developing Android Applications
• http://training.oreilly.com/androidapps/
• http://training.oreilly.com/androidapps2/
• Tech Reviewer:

3. Preliminaries
Getting Git and Getting Set Up

4. What’s a Git?
A completely ignorant, childish person with no manners.
- http://urbandictionary.com
Linus Torvalds
http://en.wikipedia.org/wiki/Linus_Torvalds

5. What’s a Git?
Git is a free & open source, distributed version
control system designed to handle everything from
small to very large projects with speed and efficiency.
- http://git-scm.com

6. Getting Set Up on Mac
• Homebrew - http://mxcl.github.com/homebrew/
• MacPorts - http://www.macports.org/

7. Getting Set Up on Windows
• msysgit -http://code.google.com/p/msysgit/
• Cygwin - http://www.cygwin.com/

8. Getting Set Up on Linux
• apt, etc - you probably know the drill

9. Gooies!
• Git Tower - http://git-tower.com M
• Brother Bard’s GitX fork -
Mac http://brotherbard.com/blog/2010/03/experimental-gitx-fork/
A
C
• Tortoise Git - http://code.google.com/p/tortoisegit/ W
Mac
I
N

10. Eclipse Integration
• http://www.eclipse.org/egit/

11. Reference
• Git - http://git-scm.com/
• ProGit - http://progit.org/book/ - Scott Chacon
• Insider Guide to Github - http://www.pragprog.com/screencasts/
v-scgithub/insider-guide-to-github - Scott Chacon

12. Note
• Code may be in backticks: `git <command>`
• Don’t input the backticks

13. The Command Line
A Short Sermon

14. Seven Use Cases
Where Git will Make your Life Easier

15. Project History
Git will Make your Life Easier

16. Why Source Control
• For the solo developer?
• Protection against mistakes
• Freedom
• to refactor
• to experiment
• For the development team?
• All of the above, plus:
• Parallel development
• Merging different code branches

17. Simple Commands
• `git init`- Creates an empty Git repository
• .gitignore - tells git to ignore certain files
• `git add` - Adds a file to the stage (“stages a file”)
• `git rm` - Removes from version control
• `git commit` - Commits the staged changes to the (local)
repository
• `git log`
• `git add -i` Interactive Add

18. git git
or clone
init
git 86650c185eda50c9f9d58e2fbdf8b7113e5dee54
git commit
changes add
git
git commit 6facfd9f34173f4fb024196996e948a87c85eb56
changes add
git
git commit b02ef5bf190e28ba24eab3ffab6133181cb5b5ef
changes add
... ∞
Simple Workflow

19. .gitignore
• Can be nested deeply
• https://github.com/github/gitignore
• Use it! Contribute!

20. Git Log - The Project’s History
• What got committed?
• Commit messages
• Content
• When? Who?

21. What’s With all the Characters?
86650c185eda50c9f9d58e2fbdf8b7113e5dee54
• SHA1 Hash
• Uniquely identifies a commit
• Secure - very unlikely that someone can tamper with content in a
repository
“... to have a probability of a SHA1-hash collision rise to 1/2,
you need about 10^24 objects ...”
- Scott Chacon in Pro Git (paraphrased)

22. Interactive Add - Building Commits
• `git add` simply adds to the stage
• `git commit -a` will commit all changes to tracked files (add and
commit)
• `git add -i` -- a command line tool to interactively add changes
• Individual commits shouldn’t leave things broken
• Try to commit some useful feature or bug fix all together

23. Getting Out of Trouble
Git will Make your Life Easier

24. Advanced Commands
• blame
• checkout
• commit -a
• reset
• stash
• commit --amend
• revert

25. git blame
• remember: git help blame
• Who broke the build??? etc...

26. git checkout, commit -a, reset
• remember: git help reset
• `git commit -a` = commit bypassing `git add`
• `git checkout <filename>` = remove all unstaged changes
• `git reset <filename>` = opposite of `git add <filename>`
• `git reset HEAD` = same as above - acts on all changes
• `git reset HEAD^` (also ^^, or ~1, ~42, etc.) = rollback commits
to working tree
• `git reset --soft` = rollback commit to stage

27. git stash
• remember: git help stash
• Stash away changes in a safe place

28. git commit --amend
• Oops! I misspelled something in the commit message
• Oops! I did `git commit -a` and forgot to `git add` a file
• Oops! I just committed a bug
• USE ONLY BEFORE YOU SHARE CHANGES

29. git revert
• Commits the reverse of a commit
• The previous commit is still there
• != svn revert

30. Collaboration
Git will Make your Life Easier

31. Remotes
• remote add
• push
• clone
• pull
• fetch

32. Strategies
• Star
• Peer to Peer
• Blessed Repository
• Hierarchical

33. Committer
Committer Committer
“The
Committer Server” Committer
Committer
Star

34. • ssh://user@computer:path/to/repo.git
• http Peer
• Gitosis
• Gitolite
Peer Peer
Peer to N Peers

35. Dictator ... etc. Maintains a “blessed repository”
Lieutenant Lieutenant
Developer Developer Developer Developer
Hierarchical (Linux model)

36. Topical Development
Git will Make your Life Easier

37. Branching
• checkout -b
• merging
• Rebasing
• cherry-pick

38. How To Think About Branching
• Topic Branches
• Mainline
• What do you want “master” to mean?
• Branching examples

39. Topic Branches
• Branching is about controlling feature sets
• Make a new branch for a story
• Make a new branch for a bug fix
• Make a new branch to spike something

40. Team Branching Strategies
• What do you want “master” to mean?
• Keep master deployable?
• one strategy for web software
• Use “master” as an integration branch?
• Each developer uses topic branches and integrates to master
• Make a branch for releases

41. Branching
git checkout -b add_login_activity
master
Mac
fb4f5d9 c5083fa
add_login_activity
Mac
9aa8827 fe594ce ccb6f5e

42. Branching: Merging
git checkout master
git merge add_login_activity
master
Mac 9aa8827 fe594ce ccb6f5e
fb4f5d9 c5083fa 3f43fa3
add_login_activity
Mac
9aa8827 fe594ce ccb6f5e

43. Branching: Rebasing
master
Mac
fb4f5d9 c5083fa 3f43fa3
add_login_activity
before Mac
9aa8827 fe594ce ccb6f5e
master
Mac
fb4f5d9 c5083fa 3f43fa3
add_login_activit
after Mac
9aa8827 fe594ce ccb6f5e
`git rebase master`

44. Branching: Rebasing
• Better than merging
• Don’t use if you’ve pushed your branch to a remote
• Git will complain about refs
• Can override with `git push -force`
• Also available on `git pull --rebase`
• Helpful for avoiding merge commits
• May cause problems if git can’t automatically merge
• `git reset HEAD` and start over with normal `git pull`

45. Cherry-pick
git cherry-pick fe594ce
A new commit
master with the changes
from fe594ce
Mac
fb4f5d9 c5083fa 3f43fa3
add_login_activity
Mac
9aa8827 fe594ce ccb6f5e

46. Cherry Picking
• Doesn’t add a reference to the old commit
• Only applies the changes
• Future merges should apply cleanly

47. Release Management
Git will Make your Life Easier

48. Tagging
• tag
• push --tags

49. Tagging
git tag -a -m"Tagging v1.0" v1.0 c5083fa
master
Mac
fb4f5d9 c5083fa 3f43fa3
• Both -v1.0 and c5083fa will point to c5083fa
• Push this tag with `git push --tags`
• Can be cryptologically signed

50. Bug Fixing
Git will Make your Life Easier

51. Bug Fixing
• blame
• bisect

52. Bisect
git bisect start HEAD
git bisect bad
fb4f5d9
Mac
c5083fa 3f43fa3 9aa8827 fe594ce ccb6f5e 2e531cb
git bisect good fb4f5d9 HEAD
fb4f5d9
Mac
c5083fa 3f43fa3 9aa8827 fe594ce ccb6f5e 2e531cb
git bisect good
Git tells you
this was the
git bisect good
first bad
git bisect bad commit
HEAD
fb4f5d9
Mac
c5083fa 3f43fa3 9aa8827 fe594ce ccb6f5e 2e531cb

53. Open Source Code
Git will Make your Life Easier

54. Github.com
• Search it!
• Forking
• Pull Requests

55. Thank you!
Git
For the Android Developer
AnDevCon 2011 : Tony Hillerson