Getting Started with Git5/17/2012

Rick Umalirickumali@gmail.comhttp://tech.rickumali.com/

This presentation is at:

http://sn.im/startgit

If you're on Google Docs, make sure to read the 'speaker notes' for this presentation.

Questions I Plan to Answer

What is source control?

What is the big deal with Git?

Can you show me a little Git?Commits. Branches. Merges. Remote repos.

What is Source Control?

A mechanism to track changes in source code.

Used for version history, auditing, and recovery.

Source code control is the most important practice a coding professional can do.

Revision Control Example: Wiki

Revision Control Example: Git

This is what we'll be trying.

Git

Git is an open source, distributed version control system designed for speed and efficiency.

● Freedom● No "server" required● Unique architecture

Installing Git

http://git-scm.com/book/en/Getting-Started-Installing-Git

The installation is very easy!

Warning: Command Line Ahead

First Time Use: Set Up

Tell Git who you are!

% git config --global user.name "Rick Umali"% git config --global user.email "rickumali@gmail.com"

Future 'commits' will show this information.

% git config --list

See "git config --help" for more configurations.

Creating a "Repository"

Let's pretend we're developing a Drupal module.

% cd web/sites/all/modules% mkdir dumpstamp% cd dumpstamp% git init

"git init" creates the entire Git repository. No server interaction required!

Committing Your First File

To 'commit' means 'to save the state' of your work. You must first 'add' this change to the 'staging area'.

% vi README.txt% git add README.txt% git commit -m "First commit. README file."

Use 'git help' to learn all the switches. -m stands for message.

Looking at the Repository

% git log

Each 'commit' contains an ID, along with the author information from earlier, and a time stamp.

% gitk

GUI tools can help you visualize the 'repo.'

Adding More Files% vi dumpstamp.info dumpstamp.module% git status% git add .% git commit

This second commit saves the work of adding two files by using 'git add .'.

The .module and .info files are the two required files for every Drupal module.

Bonus: Creating a Module% drush pm-info dumpstamp

% drush enable dumpstamp

Examining Changes to Files% vi dumpstamp.module% git status% git diff% git add dumpstamp.module% git commit% git log

The above is a typical 'workflow'.

Git offers suggestions and hints as you use it.

Doing More Changes% vi dumpstamp.module% git diff% git commit -a

Or even:

% git commit -a -m "Commit message."

Another typical 'workflow'.

Looking at the Log Again

The history can be examined different ways.

% git log% git log --format=short% git log --format=oneline% git log --oneline

Revisiting History

You can 'revisit' any point of your history.

% git checkout SHAID

Every commit is known by its SHA ID.

This is the first step in making a branch! (Use git checkout master to revert.)

Branching and Merging Next, But...

What we have covered so far is probably 70-80% of what you will do with git.

Adding and committing files are the heart of git (and any version control system).

Git encourages experimentation, by making branching very easy.

Branching

Branching: git checkout -b

% git checkout -b BRANCH SHA1

Make some edits on a change below the master, then commit.

git branch makes a branch from the branch you're on (default branch is 'master').

Branching: Starting State

SHA 1Amaster

NOTE: 'master' is a branch that's created 'by default'.

Branching: Make Some Changes

SHA 1A

SHA 2Bmaster

git commit

Branching: Making a Branch

SHA 1A

SHA 2Bmaster

branch1

git checkout -b branch1 SHA1

NOTE: This command is a short cut for: git branch branch1 name_of_branch , then git checkout branch1 .

Branching: Changes on the Branch

SHA 1A

SHA 2Bmaster branch1SHA 3C

(Make changes in branch1.)git commit

Visualizing the Branches

Merging

Bringing two branches together.

Git calculates the correct 'merge base'.

First 'checkout' the branch you want to merge into (typically master), then 'merge' the branch.

% git checkout master% git merge BRANCH

Merging: Starting State

SHA 1A

SHA 2Bmaster branch1SHA 3C

git branch

Merging: Two Steps

SHA 1A

SHA 2B

master

branch1SHA 3C

SHA 4D

git checkout mastergit merge branch1

Merging: The Hard Part

Manual 'merging' may be required.

Visualizing the Merge

Whew!

Remote Branches

You can 'browse' public Git repositories for code that you want to examine or use.

You can upload a local Git repository to a public Git repository.

Common Public Git Repositories

Browsing and Grabbing Code

git clone git@github.com:rickumali/RickUmaliVanityWebsite.git

Uploading Code (to Github)

Create a key pair on your machine.

Create a repository (on Github).

Add a 'remote' (via git remote add).

Upload your code (via git push).

Creating a Key Pair

Creating a Repository

Adding a Remote, then Upload

After An Upload (to Github)

git clone git@github.com:rickumali/DumpStamp.git

Next Steps

Install Git.

Commit your code changes frequently.

Log verbosely (in commit messages).

Experiment (branch) often.

Resources

http://git-scm.org/Both "Pro Git" book, and Git reference

http://gitref.org/A "quicker" Git reference

http://www-cs-students.stanford.edu/~blynn/gitmagic/"Friendlier" Git walk-through (git magic).

http://drupal.org/node/803746A workflow for using Git with Drupal.

http://www.mail-archive.com/dri-devel@lists.sourceforge.net/msg39091.html

Linus on "clean history."

Resources

http://www.youtube.com/watch?v=4XpnKHJAok8Linus Torvalds (Git creator) (May '07)

http://www.youtube.com/watch?v=8dhZ9BXQgc4Randal Schwartz (Perl expert and Git old-timer) (Oct

'07)http://www.youtube.com/watch?v=ZDR433b0HJY

Scott Chacon (Pro Git author) (July '11)

Getting Started with Git

Rick Umalirickumali@gmail.comhttp://tech.rickumali.com/

Thank you!