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