Git Collaboration

...Coding is better, together

Updated By Alex Niderberg / @AlexNiderbergMaster Software Engineer @ Capital One Labs

Software Development Life Cycle

What is Git?

• distributed version control system
• allows you to work off-line
• provides a collaboration framework
• "the stupid content tracker"

Linus 2007 git overview

Source: Linus 2007 Git Introduction

Centralized VCS

Source: Illustrated Distributed Version Control

Distributed VCS

Source: Illustrated Distributed Version Control

Animation Demo

Key Git Concepts

• Staging Area / Working Copy
• Commit Object
• .git repository
• Branches
• Stashing
• MergingAre git and github the same?

Edit / Stage / Commit

What does commit object hold?

• reference to parent commit, if any
• tree - set of files conveying current state of the project
• author info, commiter info, commit message, etc. Commit object is uniquely identified by a 40-character SHA1 hash

Git Repository

Git stores information about your project in .git subdirectory referred to repository

What does .git include?

• commit objects
• HEAD - a set of reference to commit objects
• ..more..

Branching

A branch is collection of commit objects When initializing a git repo the default branch is master

    (1) -- (2) -- (3)
                   |
                 master
                   |
                  HEAD

Stashing

Switching to a new branch

    # creates a new branch
    $ git branch [new-branch-name] 
    # move HEAD to point to new branch
    $ git checkout [new-branch-name] 

    $ git checkout -b [new-branch-name]

Example workflow

• Create a new branch
• Make code changes
• Commit changes
• Run tests on code
• If test success merge those changes back to master branch

Merging

$ git merge [branch-name]

Before merging

                        bug-fix 
                          |
             +----(4)----(5)
            /             
  (1) -- (2) -- (3)
                 |
               master
                 |
                HEAD

$ git merge bug-fix

                        bug-fix 
                          |
             +----(4)----(5)+
            /                \
  (1) -- (2) -- (3)----------(6)
                              |
                            master
                              |
                             HEAD

Git in Action

• Status
• Init
• Clone
• Diff
• Commit

Check for git repo

$git status
fatal: Not a git repository (or any of the 
parent directories): .git

Initializing Repository

$ mkdir [project-name]
$ cd [project-name]
$ git init

git-collab/
  .git/
    config
    description
    HEAD
    hooks/
    info/
    objects/
    refs/

Cloning existing repository

$ git clone [git-url]
$ git clone https://github.com/vmaliwal/git-collab.git

Untracked Changes / Files

$ git status
On branch master
Your branch is up-to-date with 'origin/master'.

Changes not staged for commit:
(use "git add <file>..." to update what will be committed)
(use "git checkout -- <file>..." to discard changes in working directory)

modified:   README.md
modified:   index.html

Untracked files:
(use "git add <file>..." to include in what will be committed)

images/CentralizedVCS.png
images/DistributedVCD.png
images/LinusViewDVCS.png

no changes added to commit (use "git add" and/or "git commit -a")
</file></file></file>

Git Diff

$ git diff README.md 
diff --git a/README.md b/README.md
index f08ca69..10ea20b 100644
- a/README.md
+ b/README.md
@@ -1 +1,9 @@
-### Introduction to Git 
\ No newline at end of file
+### Introduction to Git 
+
+- run
+```
+npm install
+grunt serve
+```
+
+- Make changes by modifying index.html
\ No newline at end of file

Creating a commit object

Create a new file or modify existing

$ echo "Introduction to Git" > README

$ git status
# On branch master
#
# Initial commit
#
# Untracked files:
#   (use "git add [file]..." 
# to include in what will be committed)
#
# README

Add

    
$ git add [file-name]
$ git commit -m "Initial commit"
    

    
$ git add . //to add all modified files, or
$ git commit -a -m "Initial commit"
    

Commit

    
Git commit -a #is the same as using git add and then git commit
git config --global color.ui true
    

Additional Git Concepts

• git config
• vim .gitignore
• git diff [ --staged | --cached ]
• git add --patch
• git [command] --help or man git

Git Config

• git config --list
• git config --global user.name "Your Name"
• git config --global user.email yourEmail@gmail.com
• git config --global push.default simple #remove verbose messaging about the git 2.0 change
• git config --global core.editor "subl -n -w" #editor for commit messages
• git commit -a #will bring up sublimetext so you can enter you commit message

.gitignore the unsung hero

Diff Options

#git diff [ --staged | --cached ]
$ git status
# At least 1 file is staged
$ git diff --staged
# Reveals the staged changes
$ git reset #to push those changes back to the working copy

Break Changes into Smaller Pieces

#git add --patch [file]
$ git add --patch
#Use s for smaller y, n, ...

Get Git Help

#git [command] --help or man git
$ git diff --help
$ man git
# Then use / to search for --ca

Collaboration

• Distributed version control model to collaborate between multiple developers.

  • Remote repository
  • Pull remote changes
  • Push local changes to remote

Remote repository

• Remote repositories are versions of your project that are hosted on the Internet or network somewhere.

  • Create a new remote repository(on github, bitbucket, etc.) and clone to your local machine. Or,
  • Add existing git repo from your local machine to remote

Create a new remote repo and clone to your local machine

• Create new remote repository on github or bitbucket

  $ git clone [git-remote-repo-url].git

• As name suggests clone command can be used to clone any remote repository

Add existing git repo from local machine to remote

Create new repository on github or bitbucket On your local machine..

$ git remote add origin [git-remote-repo-url].git
$ git push -u origin master

origin is a remote repository reference that git uses

Pulling remote changes

$ git pull [remote-repo-reference] [remote-branch-name]
$ git pull origin master

Pushing changes to remote

$ git push [remote-repo-reference] [remote-branch-name]
$ git push origin master

Multiple Remotes

origin  https://github.com/aln787/git-collab.git (fetch)
origin  https://github.com/aln787/git-collab.git (push)
14109fd767af:git-collab xvo202$ git remote add kdc https://github.kdc.capitalone.com/xvo202/git-collab.git
14109fd767af:git-collab xvo202$ git remote -v
kdc https://github.kdc.capitalone.com/xvo202/git-collab.git (fetch)
kdc https://github.kdc.capitalone.com/xvo202/git-collab.git (push)
origin  https://github.com/aln787/git-collab.git (fetch)
origin  https://github.com/aln787/git-collab.git (push)

Fork and Pull

Fork Exercise

Merge conflicts

While pulling or merging a branch merge conflicts can occur due to conflicting changes

$ git checkout -b develop

$ git branch
* develop
  master 

$ git checkout master

$ git merge develop
Auto-merging app.js
CONFLICT (content): Merge conflict in app.js
Automatic merge failed; fix conflicts and then commit the result.

$ git merge-tool

Tips and Tricks

If you are ever unsure what to do when using Git, copy your project directory.

Setting Up SSH Keys

$ ls -al ~/.ssh
$ ssh-keygen -t rsa -b 4096 -C "youremail@email.com"
$ eval "$(ssh-agent -s)"
$ ssh-add ~/.ssh/id_summit2016
$ cat ~/.ssh/id_summit2016.pub 

$ ssh -T git@github.com

Additional Git Commands

• git diff HEAD^ --word-diff
  • git config --global help.autocorrect1
• git config --global color.ui 1
• git commit --amend -C HEAD
  • Use this to add changes you forgot to add to the last commit that are currently staged