For the Android DeveloperAnDevCon 2011 : Tony Hillerson#AnDevCon #effectiveuihttp://www.slideshare.net/thillerson/scm-for-android-developers-using-git

Git

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:

PreliminariesGetting Git and Getting Set Up

What’s a Git?

A completely ignorant, childish person with no manners.- http://urbandictionary.com

Linus Torvaldshttp://en.wikipedia.org/wiki/Linus_Torvalds

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

Getting Set Up on Mac• Homebrew - http://mxcl.github.com/homebrew/

• MacPorts - http://www.macports.org/

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

• Cygwin - http://www.cygwin.com/

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

Mac

WIN

Mac

MAC

Gooies!• Git Tower - http://git-tower.com

• Brother Bard’s GitX fork - http://brotherbard.com/blog/2010/03/experimental-gitx-fork/

• Tortoise Git - http://code.google.com/p/tortoisegit/

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

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

Note• Code may be in backticks: `git <command>`

• Don’t input the backticks

The Command LineA Short Sermon

Seven Use CasesWhere Git will Make your Life Easier

Project HistoryGit will Make your Life Easier

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

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

or

Simple Workflow

gitinit

changes

gitadd git commit

changes

gitadd git commit

changes

gitadd git commit

... ∞

86650c185eda50c9f9d58e2fbdf8b7113e5dee54

6facfd9f34173f4fb024196996e948a87c85eb56

b02ef5bf190e28ba24eab3ffab6133181cb5b5ef

gitclone

.gitignore• Can be nested deeply

• https://github.com/github/gitignore

• Use it! Contribute!

Git Log - The Project’s History• What got committed?

• Commit messages

• Content

• When? Who?

What’s With all the Characters?

“... 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)

86650c185eda50c9f9d58e2fbdf8b7113e5dee54• SHA1 Hash

• Uniquely identifies a commit

• Secure - very unlikely that someone can tamper with content in a repository

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

Getting Out of TroubleGit will Make your Life Easier

Advanced Commands• blame

• checkout

• commit -a

• reset

• stash

• commit --amend

• revert

git blame

• remember: git help blame

• Who broke the build??? etc...

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

git stash

• remember: git help stash

• Stash away changes in a safe place

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

git revert

• Commits the reverse of a commit

• The previous commit is still there

• != svn revert

CollaborationGit will Make your Life Easier

Remotes• remote add

• push

• clone

• pull

• fetch

Strategies• Star

• Peer to Peer

• Blessed Repository

• Hierarchical

Star

“The Server”Committer

Committer

Committer

Committer

Committer

Committer

• ssh://user@computer:path/to/repo.git

• http

• Gitosis

• Gitolite

Peer to N Peers

Peer Peer

Peer

Hierarchical (Linux model)

Developer Developer

Lieutenant

Developer Developer

Lieutenant

Dictator ... etc. Maintains a “blessed repository”

Topical DevelopmentGit will Make your Life Easier

Branching• checkout -b

• merging

• Rebasing

• cherry-pick

How To Think About Branching• Topic Branches

• Mainline

• What do you want “master” to mean?

• Branching examples

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

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

Mac

add_login_activity

Mac

master

Branching

fb4f5d9 c5083fa

9aa8827 fe594ce ccb6f5e

git checkout -b add_login_activity

Mac

add_login_activity

Mac

master

Branching: Merging

fb4f5d9 c5083fa

9aa8827 fe594ce ccb6f5e

3f43fa3

git checkout master

9aa8827 fe594ce ccb6f5e

git merge add_login_activity

Mac

add_login_activity

Mac

master

Branching: Rebasing

fb4f5d9 c5083fa

9aa8827 fe594ce ccb6f5e

3f43fa3

Mac

add_login_activit

Mac

master

fb4f5d9 c5083fa

9aa8827 fe594ce ccb6f5e

3f43fa3

after`git rebase master`

before

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`

Mac

add_login_activity

Mac

master

Cherry-pick

fb4f5d9 c5083fa

9aa8827 fe594ce ccb6f5e

3f43fa3

git cherry-pick fe594ce

A new commit with the changes

from fe594ce

Cherry Picking• Doesn’t add a reference to the old commit

• Only applies the changes

• Future merges should apply cleanly

Release ManagementGit will Make your Life Easier

Tagging• tag

• push --tags

Mac

master

Tagging

fb4f5d9 c5083fa 3f43fa3

git tag -a -m"Tagging v1.0" v1.0 c5083fa

• Both -v1.0 and c5083fa will point to c5083fa

• Push this tag with `git push --tags`

• Can be cryptologically signed

Bug FixingGit will Make your Life Easier

Bug Fixing• blame

• bisect

Bisectgit bisect start

Macfb4f5d9 c5083fa 3f43fa3 9aa8827 fe594ce ccb6f5e 2e531cb

git bisect bad

Macfb4f5d9 c5083fa 3f43fa3 9aa8827 fe594ce ccb6f5e 2e531cb

git bisect good fb4f5d9

Macfb4f5d9 c5083fa 3f43fa3 9aa8827 fe594ce ccb6f5e 2e531cb

git bisect goodgit bisect goodgit bisect bad

Git tells you this was the first bad commit

HEAD

HEAD

HEAD

Open Source CodeGit will Make your Life Easier

Github.com• Search it!

• Forking

• Pull Requests

Thank you!

For the Android DeveloperAnDevCon 2011 : Tony Hillerson

Git