Creating a Repository

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:

$ mkdir inflammation
$ cd inflammation

Then we tell Git to make inflammation 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 planets 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

If you are using a different version of git than I am, then then the exact wording of the output might be slightly different.

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

Places to Create Git Repositories

Jane starts a new project, infection, related to her inflammation project. Despite Samit’s concerns, ahe enters the following sequence of commands to create one Git repository inside another:

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

Why is it a bad idea to do this? (Notice here that the inflammation project is now also tracking the entire infection repository.) How can Jane undo her 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 as shown above:

$ 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 repository:

$ touch patient1 patient2 patient3 patient4        # create infection files
$ cd ..                                            # return to infection directory
$ ls infection                                     # list contents of the infection directory
$ git add infection/*                              # add all contents of inflammation/infection
$ git status                                       # show infection files in staging area
$ git commit -m "add patient files"                # commit inflammation/infection to inflammation Git repository

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

$ nano .gitignore # open the .gitignore file in the text editor to add the moons directory
$ cat .gitignore # if you run cat afterwards, it should look like this:

infection

To recover from this little mistake, Jane can just remove the .git folder in the infection subdirectory. To do so she can run the following command from inside the infection 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.