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Presentation notes from JMU Unix Users Group meetings

JMU UUG git Tutorial

Creating a GitHub account

GitHub, even with it’s flaws, is the primary website for sharing and uploading your code with git. They also have a great student pack which gives you all kinds of great benefits.

Other services that will host your git repositories include:

All services have different pros and cons. Some allow you to use private repositories for free, some are open source, and some cost money. Make sure to evaluate all options to decide which is best for you. For tonight, we will be using GitHub since, at the moment, it is the most popular.

Creating a repository on the GitHub website

Using the + button in the top right corner or the webpage, choose “New Repository”. Pick a name and optionally a description. For this tutorial, we will not be using a pre-provided README, .gitignore, or license. We may these at future UUG sessions.

Once you create the repository you will get a page with a bunch of commands that GitHub wants you to run. Select the HTTPS button towards the top of this guide, and notice the line starting with git remote add origin. You don’t need to do anything with this now. Just keep the page open.

Starting your first git repository

First, we will create a directory to use for this tutorial.

mkdir -p ~/UUG/uug-git-intro && cd $_

If we try to use a git command here, we will get an error

git commit -am "Test commit"

Notice that you got an error when you tried to do this! You cannot create a commit in git without that directory being a part of a git repository.

So let’s initialize your git repository. This starts getting git set up to run.

git init

If you run ls -al, you will now see a .git directory there. This is where git stores all of the data about your repository.

You now have to tell git where your code should be pushed to. We are using GitHub for this and we’ll now we will use that command from earlier.

git add remote origin https://github.com/YOURUSERNAME/REPONAME.git

This has created a .git folder, with all the information about your repository.

ls -a
ls .git

Basic git configuration

By default, git will have your name and email configured to be your login name@hostname. This is nice in some ways, but probably not your actual email address. Let’s fix this.

git config --global user.name "Your Name"
git config --global user.email "your@email.address"
git config --global color.ui true

Now git will always know who you are, and this information will be in all your commits.

Making your first commit

Commits are basically a record of changes to your directory. Each time you make a change, you need to tell git to create a new record. You do this with the commit command.

Before you commit, you have to make a change to the directory. Let’s create a file

vim README.txt

Now that we have modified a file, we can ask git to tell us the status of of our directory.

git status

And if we want git to tell exactly what’s different, in the file, it can do that too.

git diff

We should instruct git to start tracking changes to our README.txt file. We also need to add it to our ‘stage’. To do this, we will use the following command.

git add README.txt

Let’s tell git to create a record of our change

git commit

Vim (or your default editor) will open. Type a description of your changes, called a commit message, and save the file (in Vim, you can type :wq in normal mode).

See a record of commits

git keeps a record of each of your changes in a log. TO see this, let’s run

git log

Reverting a commit

As you’re making changes, you very often will want to undo one of your previous commits. git allows for this with its revert command.

Let’s modify our directory and commit that change.

rm README.txt
git commit -a

Later, we realize that we regret this change. We can undo this. The way that reverting works in git is by taking the state of the repository at a point in time and bringing it back to the present.

So what we need to do is check our log, and find the hash of the commit we want to revert

git log
git revert "hash"

This will create a commit with the default message, ‘Revert “Old Commit”’. Push this change back to GitHub with

git push

Going futher

For an extension of this presentation and further examples and exercises in using Git, checkout out the Git 201 repository.

For a git reference, check out GitHub’s Git cheat sheet