Tuesday, April 30, 2013

Git tutorial

Git is a distributed version control system which means that it does not require a central server to store all the data, unlike SVN or CVS. In practice, there is usually a central repository (remote repository, typically hosted on the internet) that one can copy (cloning). When cloning an existing repository , the user grabs the whole working tree. If you'd like to create a branch for instance to work on a specific part of your code in parallel, the branch will be local. The central copy does not need to have a counterpart.

Linux kernel's project is using git as its version control system. Some of the following commands may be useful :

Create a Git repository

# Run it in your development directory
git init
This folder will then contain a .git directory containing the complete history of the repository and .git/config will store the local configuration for it.

Add files to the repository

# Replace . by the file name if you're not planning to add all files
git add .
The marked files have been added to the staging area. It means that they will be part of the next commit. All of your modified files need to be staged (added) so that they will be included in the next commit.

Check repository status

git status
You will see which files have been modified, which ones are staged and which are not, conflicts, etc...

Commit files to the repository

git commit -m "Commit message"

Trace back your modifications

git log
You will see the list of your commits and your activity in your working tree.

Move / Rename a file

git mv <orignial file path> <new file path>

Remove a file from repository

git rm <file name>
Note : you can also simply delete the file manually. In this case, you have to add the '-a' option to the commit command to take the deletion into account.

Remove a file from staging area

git reset <file name>

Working with Remote Repositories

Ok, now we got the basics, how do we synchronize our work with others ? In the example above, we started from scratch, and our repository is local. What if somebody would like to copy it ?

Clone a remote repository

Imagine that we created a repo in a folder named "original_repo". Let's move back and create a new folder :
cd ..
mkdir clone_repo
cd clone_repo
Once we're here, we will clone the "original_repo" into "clone_repo" :
git clone ../original_repo.git .
Note : A git repository address always end with a ".git" extension.
Note 2 : If you omit the '.' at the end of the command, git will create a directory named like the origin (here 'original_repo'), move into it and pull the files from there.

If the git repository is hosted on the web, it is almost the same :
git clone https://linux389pi@bitbucket.org/linux389pi/linux389pi.git

Push changes to a remote repository


You probably noticed that git commit does not mirror your modifications on the remote repository. Instead, it creates a local commit object (snapshot). To send your modification to the central repository, you will have to push your local repository:
git push

Pull changes from the remote repository

The opposite action of pushing is pulling. You will synchronize your repository with the central one by pulling :
git pull

If you are looking for more information about git, check this link :

Git - Book 

If you are also willing to experiment git with a very cool tutorial, here is the link :

Git in practice 

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