In order to do anything in Git, you need to have a Git repository. This is where Git stores the data for the snapshots you are saving.

There are two main ways to get a Git repository. One way is to simply initialize a new one from an existing directory, such as a new project or a project new to source control. The second way is to clone one from a public Git repository, as you would do if you wanted a copy or wanted to work with someone on a project. We will cover both of these here.

To create a repository from an existing directory of files, you can simply run git init in that directory. For example, let's say we have a directory with a few files in it, like this:

$ cd konnichiwa
$ ls
README   hello.rb

This is a project where we are writing examples of the "Hello World" program in every language. So far, we just have Ruby, but hey, it's a start. To start version controlling this with Git, we can simply run git init.

$ git init
Initialized empty Git repository in /opt/konnichiwa/.git/

Now you can see that there is a .git subdirectory in your project. This is your Git repository where all the data of your project snapshots are stored.

$ ls -a
.        ..       .git     README   hello.rb

Congratulations, you now have a skeleton Git repository and can start snapshotting your project.

In a nutshell, you use git init to make an existing directory of content into a new Git repository. You can do this in any directory at any time, completely locally.

If you need to collaborate with someone on a project, or if you want to get a copy of a project so you can look at or use the code, you will clone it. You simply run the git clone [url] command with the URL of the project you want to copy.

$ git clone git://github.com/schacon/simplegit.git
Initialized empty Git repository in /private/tmp/simplegit/.git/
remote: Counting objects: 100, done.
remote: Compressing objects: 100% (86/86), done.
remote: Total 100 (delta 35), reused 0 (delta 0)
Receiving objects: 100% (100/100), 9.51 KiB, done.
Resolving deltas: 100% (35/35), done.
$ cd simplegit/
$ ls
README   Rakefile lib

This will copy the entire history of that project so you have it locally and it will give you a working directory of the main branch of that project so you can look at the code or start editing it. If you change into the new directory, you can see the .git subdirectory - that is where all the project data is.

$ ls -a
.        ..       .git     README   Rakefile lib
$ cd .git
$ ls
HEAD        description info        packed-refs
branches    hooks       logs        refs
config      index       objects

By default, Git will create a directory that is the same name as the project in the URL you give it - basically whatever is after the last slash of the URL. If you want something different, you can just put it at the end of the command, after the URL.

In a nutshell, you use git clone to get a local copy of a Git repository so you can look at it or start modifying it.