Etymology: From Middle English get ("offspring", especially "illegitimate offspring"). A southern variant of Scots get ("illegitimate child, brat"), related to beget. (from Online Etymology Dictionary)
Meaning (Britain, slang, pejorative): 1) A contemptible person 2) A silly, incompetent, stupid, annoying or childish person.
Seriously speaking, Git is a powerful version control system, Developed by Linus Torvalds in 2005 and introduced to the Open Source community as "the information manager from hell" (Linus Torvalds).
As Linux, it's named after his creator:
“I’m an egotistical bastard, and I name all my projects after myself. First Linux, now git.”
We are going to use Git from the command line. Without any arguments, Git (git.exe) lists its options and the most common subcommands.
To manage our web applications, we are going to use the following subcommands:
add Add file contents to the index
branch List, create, or delete branches
checkout Checkout and switch to a branch
clone Clone a repository into a new directory
commit Record changes to the repository
diff Show changes between commits, the commit and working trees, etc
log Show commit logs
init Create an empty git repository or reinitialize an existing one
merge Join two or more development histories
mv Move or rename a file, a directory, or a symlink
pull Fetch from and merge with another repository or a local branch
push Update remote refs along with associated objects
rm Remove files from the working tree and from the index
show Show various types of objects
status Show the working tree status
You do not need to understand these commands now, but we will be using them shortly for our lab activities.
As you may immagine, there is more than one way to use Git. The following slides are an example of one way in which you can use Git and assume that you are using the git command from the shell.
Documentation for each git subcommand is available using any of the following commands:
git help subcommand git --help subcommand git subcommand --help
git clone git://github.com/Project/project.git
We will download the phpDocumentor package (we will also use the package later on this semester).
phpdoc run -h
(just to test that the package has been downloaded correctly)
To create a Git repository, you can run git init in the root folder of your project:
This creates a .git subfolder with the information Git needs to operate.
For the aims of this course, each team has an allocated space on GitHub.
Register on GitHub here: https://education.github.com/pack, using your institutional email address and then ask your lecturer (in the lab) to add your group members to your group's github private repository.
Once you have been added to the repository, your repository name will be the same as your group numer. E.g. if you are "Group1" your repository URL is https://github.com/uel-webapps/group1.git
You do not need to create an initial repository, but read the getting started with GitHub guide and explore the web interface for GitHub by opening your repository pages.
Authentication in git is done using a public/private key combination.
You can use your own key pair or create a new one:
ssh-keygen -t rsa -b 4096 -C "email@example.com"
After creating the keypair, you will use ssh-agent to keep the key pair in memory. This is needed for authentication.
eval "$(ssh-agent -s)" ssh-add ~/.ssh/id_rsa
You will also need to upload your keypair on GitHub, here: https://github.com/settings/ssh
Create your keypair and run
ssh-agent to load the keypair.
Follow the step-by-step instructions here and upload the public key to GitHub.
Beside setting your public/private key, before you start using Git you need to set up your username, and your email. This will be the default value used for all your commits.
git config --global user.name "Andres Baravalle" git config --global user.email "firstname.lastname@example.org"
This will save the info in
$HOME/.gitconfig - you need to run this operation only once.
Set up the username, email (on the Linux shell) and download your initial (empty) repository from GitHub.
git clone email@example.com:uel-webapps/group1.git
(replace the address as needed)
All repositories are empty by default. You must explicitly add content to your repository - using
git add and
When you add content to the repository, it will be tracked.
echo "<html><head><title>Hello world</title></head><body><p>Hello world</p></body></html>" >hello.php git add hello.php echo "<html><head><title>Hello world</title></head><body><p>Hello world</p></body></html>" >hello2.php git add hello2.php
git add puts the file into the stage; Git now knows that the file will have to be uploaded into the repository during the next commit.
git commit -m "Initial commit"
You can see the log of your commits using:
To see more details about a particular commit, use git show with a commit id (or just git show for the last one).
After adding (git add) and committing (git commit) operations, the code has not been yet uploaded to the repository.
You need to do that with:
git addadds your modified files to the queue to be committed later. Files are not committed
git commitcommits the files that have been added and creates a new revision with a log. If you do not add any files, git will not commit anything. You can combine both actions with
git commit -a
git pushpushes your changes to the remote repository.
Create a hello word PHP file, add it to the repository, commit and push.
If you are working as part of a team, another team member could have changed one or more files in the project that you also have changed.
This is normally signalled by this type of error:
error: failed to push some refs to 'firstname.lastname@example.org:uel-webapps/andres.git' To prevent you from losing history, non-fast-forward updates were rejected Merge the remote changes before pushing again. See the 'Note about fast-forwards' section of 'git push --help' for details.
When this happens, pull the repository (or branch of the repository):
Your file(s) will be updated and will include both versions; fix and push, using --force.
To see the differences between the two revisions of index.html, recall both full commit
ID names (use
to get the ids) and run
git diff 9da581d910c9c4ac93557ca4859e767f5caf5169 ec232cddfb94e0dfd5b5855af8ded7f5eb5c90d6
To remove (delete) files from the repository, use git rm:
git rm hello.php git commit -m "Removed the first Hello World file"
Git includes the concept of branch (a separate line of development within a project) and tag (a static pointer to a specific commit).
For example, if you want to identify a specific release of your project, you use a tag (v3.2.1). If you want to identify a development vs a stable line of development, you will use a branch.
To tag a git commit, use the command git tag just after the commit:
git tag 0.1
Will tag the current commit as 0.1.
To do this ex post, identify the commit that you want to tag, using:
git log --pretty=oneline
and then run:
git tag -a v1.2 <commit id>
(replace <commit it> with the id of the commit)
Try using TortoiseGit; the interface is fairly user friendly.
You will recognise all the commands from the slides.
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