What is git?

a Distributed VCS (Version Control System):

Every local copy contains the whole content of the "central" repository

No Network Needed for:

• Performing a diff
• Viewing file history
• Committing changes
• Merging branches
• Obtaining any other revision of a file
• Switching branches

You can now code in the bus / train / plane / boat

Git stores Snapshots, Not Differences

Where other VCS record Deltas to rebuild the complete files, GIT stores snapshots of modified files.

SVN:

Git stores Snapshots, Not Differences

Advantages on other VCS

Git aims at proposing:

• Speed
• Simple design
• Strong support for non-linear development (thousands of parallel branches)
• Fully distributed
• Able to handle large projects like the Linux kernel efficiently (speed and data size)

Indeed Git is fast: operations are almost instantaneous

The entire history is accessible offline

Branching is not scary. Actually, branching is the essence of Git. It so easy and flexible that we create several branches every day.

Setting-up Git working

Installation on Windows

Download it from http://git-scm.com/download/win

Add a GUI on top, or use the command line

Installation on linux

Add a GUI on top, or use the command line

Installation on a Mac

Use your favorite package installer, or refer to standard git-scm procedure

Commits

how to commit

git commit -a

Enter a commit comment

Commit is now in the history

log

Show the history of a repository

git log

commit fc365c472c195e40d8f4b6278b17a88750e81a92
Author: Baptiste Mesta <baptiste.mesta@gmail.com>
Date:   Wed Jan 13 16:04:29 2016 +0100

    added images

commit 5cce7520f99b6a4cba3997cf8f3d275086bef6f0
Author: Baptiste Mesta <baptiste.mesta@gmail.com>
Date:   Wed Jan 13 16:02:40 2016 +0100

    Added slides on git commit

commit 58782ccae98c181c68f3297b9d08ae7aed0e2844
Author: Baptiste Mesta <baptiste.mesta@gmail.com>
Date:   Wed Jan 13 15:13:01 2016 +0100

    add section working with git

	

but having a graphical interface is better...

Adding file to commit

the staging area is a buffer where you define what will be in the next commit

before adding

$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:   presentation/index.html

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

		presentation/images/staging.png

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

after git add --all

$git status
On branch master
Your branch is up-to-date with 'origin/master'.
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

	new file:   presentation/images/staging.png
	modified:   presentation/index.html
						

you can now commit using git commit

Branch and tag

A branch is simple pointer to a commit, that is why a branch is git is very light

A branch can be created using git branch branch_name

Then get is usinggit checkout branch_name

When a commit is done on a branch it changes where the branch point to

$ git checkout iss53
$ vim index.html
$ git commit -a -m 'add a new footer [issue 53]'
						

tag

tags are like branch but they do not move

merge

you can merge a branch into an other branch with git merge branch_name

$ git checkout master
$ git merge iss53
 Auto-merging README
Merge made by the 'recursive' strategy.
 README | 1 +
 1 file changed, 1 insertion(+)
 								

rebase

rebase is 'moving' a branch and all its commit to an other starting point

$ git checkout experiment
$ git rebase master
First, rewinding head to replay your work on top of it...
Applying: added staged command
 								

Working with remote repository

The local repository can fetch and push commits to an other repository

fetch pull and push

these command allow interaction the remote repository

fetch and pull

git fetch retrieve changes from a remote repository but do not change the working copyit only update remote branches, e.g. origin/master

git merge without more argument merge the current branch with the branch it tracks

git pull is used more often, it is a shortcut that does git fetch and git merge it can be used with the option --rebase that redo the local commit starting from the new remote position

it often happend to be like this, you made local commit and someone else pushed commit to the remote repository

the git fetch retrieve changes

You can now choose to merge or rebase you local changes

Github

GitHub is a Web-based Git repository hosting service

Cloning a remote repository

$ git clone git@github.com:bonitasoft/bonita-engine.git

Forking a remote repository

When you don't have right access to the repository in which you want to make changes

Go to Github and click Fork

You then have a copy of the repo on which you can commit, create branches, and ...

Pull Request

A PR is a request for changes to be applied in a specific branch

Pull Request - use case

You want to change something somewhere in the code. You may not have the rights to commit on this repository You may have the rights to commit but want your changes to be reviewed and commented before applying.

Practical example