Introduction to Git10/2/2013

Rick Umalirickumali@gmail.com

@rickumalihttp://tech.rickumali.com/

This presentation is on Google Drive at:

http://sn.im/git-talk-2013

There you can read the 'speaker notes' for this presentation.

What is Source Control?

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

A mechanism to track changes in source code.

Used for version history, auditing, and recovery.

Revision Control Example: Wiki

Revision Control Example: Git

You’ll learn how to make a repository like this.

Git

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

Freedom

No "server" required

Unique architecture

Warning: Command Line Ahead

Our Example: A Basic Drupal Module

Creating a Repository

% 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."

Commit often!

Looking at the Repository History

% git log% gitk

Adding More Files

% vi dumpstamp.info dumpstamp.module

% git status

% git add .

% git commit

or

% git commit -a -m “My commit message.”

Learn the shortcuts by reading Git docs.

Examining Changes to Files

% vi dumpstamp.module

% git status

% git diff

% git add dumpstamp.module

% git commit

% git log

Become familiar with Git status and diff output.

Make your commit messages meaningful!

Looking at the Log Again

The history can be examined different ways.

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

Revisiting History

You can 'revisit' any point of your history.

% git checkout SHA_ID

Checkout makes the working directory match the state of the specific SHA_ID.

This is a time machine!

Returning to the Present

At all times, Git retains a pointer to the ‘present’.

% git checkout master

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 branch

% git branch BRANCH% git checkout BRANCH

This makes a branch from “where you currently are”, and then “switches” (checks out) the branch.

“git branch” tells you what branch you’re on.

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 branch branch1git checkout branch1

OR git checkout -b branch1

Branching: Changes on the Branch

SHA 1A

SHA 2Bmaster

SHA 3C

(Make changes in "branch1".)git commit

branch1

Branching: Making a New Branch

SHA 1A

SHA 2Bmaster

SHA 3C

git checkout mastergit checkout -b branch2

branch1

branch2

Branching: Changes on another Branch

SHA 1A

SHA 2Bmaster

branch2SHA 4D

(Make changes in "branch2".)git commit

branch1 SHA 3C

Visualizing the Branches

Merging

Bringing two branches together.

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

% git checkout master% git merge BRANCH

Merging: Starting State

SHA 1A

SHA 2Bmaster

branch2SHA 4Dbranch1 SHA 3C

Merging: Fast-Forward Merge

git checkout mastergit merge branch1

SHA 1A

SHA 2B

branch2SHA 4Cmaster, branch1 SHA 3C

Merging: Resolving Conflicts

git merge branch2

SHA 1A

SHA 2B

branch2SHA 4Cbranch1 SHA 3C

SHA 5 master

Merging: The Hard Part

Manual 'merging' may be required.

Visualizing the Merge

Whew!

Using Git “Remotely”

You can upload your local Git repository to a public Git repository. These repositories are known as remotes.

Using “remotes” is the key to collaborating.

Visualizing Remotes

Your Repo Bob Repo

GitHub Repo

Uploading New Code to GitHub

Create a repository (on GitHub).

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

Upload your code (via git push).

Creating a Repository

git init

Adding a Remote

git remote adds a name for a repo at a specific URLgit remote add origin git@github.com:rickumali/DumpStamp.git

Your Repo GitHub Repo(origin)

Dumpstamp.git

This is just a naming step!

Push Your Repo to the Remote

% git push -u origin master

Visualizing the Push

git push uploads the repository to the remote

Your Repo GitHub Repo(origin)

Visualizing Remotes (cloning)

Your Repo Bob Repo

GitHub Repo(origin)

Now Bob can ‘clone’ your repository

clone

Cloning

After the Clone

The Cycle with Remotes

Your Repo Bob Repo

GitHub Repo(origin)

You Push, Bob “Pulls” (or Fetches/Merges)

pullpush

You Saw and Learned A Lot About Git

Typical Git CommandsAdd, Commit, Log, Diff, Status

Branch and Merging

Git Remote Repositories

Next Steps

Install Git

Commit frequently and log verbosely

Experiment (branch) often

Introduction to Git10/2/2013

Rick Umalirickumali@gmail.com

@rickumalihttp://tech.rickumali.com/

This presentation is on Google Drive at:

http://sn.im/git-talk-2013

There you can read the 'speaker notes' for this presentation.

Resources

http://sethrobertson.github.io/GitBestPractices/Great list of Git best practices.

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://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)