Overview

Teaching: 10 min
Exercises: 0 min

Questions

• Where does Git store information?

Objectives

• Create a local Git repository.

Once Git is configured, we can start using it. Let’s create a directory for our work and then move into that directory. For today, we’ll be working on a simple Python program. Let’s call the project “myproject”.

$ mkdir myproject
$ cd myproject

Then we tell Git to make myproject a repository — a place where Git can store versions of our files:

$ git init

If we use ls to show the directory’s contents, it appears that nothing has changed:

$ ls

But if we add the -a flag to show everything, we can see that Git has created a hidden directory within myproject called .git:

$ ls -a

.	..	.git

Git stores information about the project in this special sub-directory. If we ever delete it, we will lose the project’s history.

We can check that everything is set up correctly by asking Git to tell us the status of our project:

$ git status

# On branch master
#
# Initial commit
#
nothing to commit (create/copy files and use "git add" to track)

Places to Create Git Repositories

Dracula starts a new project, sphere_calc, related to his myproject project. Despite his colleague’s concerns, he enters the following sequence of commands to create one Git repository inside another:

$ cd               # return to home directory
$ mkdir myproject  # make a new directory myproject
$ cd myproject     # go into myproject
$ git init         # make the myproject directory a Git repository
$ mkdir sphere_calc    # make a sub-directory myproject/sphere_calc
$ cd sphere_calc       # go into myproject/sphere_calc
$ git init         # make the sphere_calc sub-directory a Git repository

Why is it a bad idea to do this? (Notice here that the myproject project is now also tracking the entire sphere_calc repository.) How can Dracula undo his last git init?

Solution

Git repositories can interfere with each other if they are “nested” in the directory of another: the outer repository will try to version-control the inner repository. Therefore, it’s best to create each new Git repository in a separate directory. To be sure that there is no conflicting repository in the directory, check the output of git status. If it looks like the following, you are good to go to create a new repository.

repository as shown:

$ git status

fatal: Not a git repository (or any of the parent directories): .git

Note that we can track files in directories within a Git:

$ touch ball.py ovoid.py       # create some sphere_calc files
$ cd ..                        # return to myproject directory
$ ls sphere_calc               # list contents of the sphere_calc directory
$ git add sphere_calc/*        # add all contents of myproject/sphere_calc
$ git status                   # show sphere_calc files in staging area
$ git commit -m "add sphere_calc files"    # commit myproject/sphere_calc to myproject Git repository

Similarly, we can ignore (as discussed later) entire directories, such as the sphere_calc directory:

$ gedit .gitignore # open the .gitignore file in the texteditor to add the sphere_calc directory
$ cat .gitignore # if you run cat afterwards, it should look like this:

sphere_calc

To recover from this little mistake, Dracula can just remove the .git folder in the sphere_calc subdirectory. To do so he can run the following command from inside the ‘sphere_calc’ directory:

$ rm -rf .git

But be careful! Running this command in the wrong directory, will remove the entire git-history of a project you might wanted to keep. Therefore, always check your current directory using the command pwd.

Key Points

• git init initializes a repository.