Creating a Repository

Last updated on 2024-03-12 | Edit this page

Overview

Questions

  • Where does Git store information?

Objectives

  • Create a local Git repository.
  • Describe the purpose of the .git directory.

We will continue with the story of Wolfman and Dracula who are investigating if it is possible to send a planetary lander to Mars.

motivatingexampleWerewolf vs dracula by b-maze / Deviant Art. Mars by European Space Agency / CC-BY-SA 3.0 IGO. Pluto / Courtesy NASA/JPL-Caltech. Mummy © Gilad Fried / The Noun Project / CC BY 3.0. Moon © Luc Viatour / https://lucnix.be / CC BY-SA 3.0.

New directory

First, let’s create a new directory in the Desktop folder for our work and then change the current working directory to the newly created one:

BASH 

cd ~/Desktop
mkdir planets
cd planets

git init

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

BASH 

git init

It is important to note that git init will create a repository that can include subdirectories and their files—there is no need to create separate repositories nested within the planets repository, whether subdirectories are present from the beginning or added later. Also, note that the creation of the planets directory and its initialization as a repository are completely separate processes.

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

BASH 

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:

BASH 

ls -a

OUTPUT 

.	..	.git

Git uses this special subdirectory to store all the information about the project, including the tracked files and sub-directories located within the project’s directory. If we ever delete the .git subdirectory, we will lose the project’s history.

Default branch

Next, we will change the default branch to be called main. This might be the default branch depending on your settings and version of git. See the setup episode for more information on this change.

BASH 

git checkout -b main

OUTPUT 

Switched to a new branch 'main'

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

BASH 

git status

OUTPUT 

On branch main

No commits yet

nothing to commit (create/copy files and use "git add" to track)

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

Places to Create Git Repositories

Along with tracking information about planets (the project we have already created), Dracula would also like to track information about moons. Despite Wolfman’s concerns, Dracula creates a moons project inside his planets project with the following sequence of commands:

BASH 

cd ~/Desktop   # return to Desktop directory
cd planets     # go into planets directory, which is already a Git repository
ls -a          # ensure the .git subdirectory is still present in the planets directory
mkdir moons    # make a subdirectory planets/moons
cd moons       # go into moons subdirectory
git init       # make the moons subdirectory a Git repository
ls -a          # ensure the .git subdirectory is present indicating we have created a new Git repository

Is the git init command, run inside the moons subdirectory, required for tracking files stored in the moons subdirectory?

No. Dracula does not need to make the moons subdirectory a Git repository because the planets repository can track any files, sub-directories, and subdirectory files under the planets directory. Thus, in order to track all information about moons, Dracula only needed to add the moons subdirectory to the planets directory.

Additionally, Git repositories can interfere with each other if they are “nested”: 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:

BASH 

git status

OUTPUT 

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

Correctinggit initMistakes

Wolfman explains to Dracula how a nested repository is redundant and may cause confusion down the road. Dracula would like to remove the nested repository. How can Dracula undo his last git init in the moons subdirectory?

Background

Removing files from a Git repository needs to be done with caution. But we have not learned yet how to tell Git to track a particular file; we will learn this in the next episode. Files that are not tracked by Git can easily be removed like any other “ordinary” files with

BASH 

rm filename

Similarly a directory can be removed using rm -r dirname or rm -rf dirname. If the files or folder being removed in this fashion are tracked by Git, then their removal becomes another change that we will need to track, as we will see in the next episode.

Solution

Git keeps all of its files in the .git directory. To recover from this little mistake, Dracula can just remove the .git folder in the moons subdirectory by running the following command from inside the planets directory:

BASH 

rm -rf moons/.git

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

Key Points

  • git init initializes a repository.
  • Git stores all of its repository data in the .git directory.