Creating a Repository

Overview

Teaching: 10 min
Exercises: 10 min

Questions

• Where does Git store information?

Objectives

• Create a local Git repository.

• Describe the purpose of the .git directory.

Once Git is configured, we can start using it.

We will help Alfredo with his new project, create a repository with all his recipes.

First, let’s create a directory in Desktop folder for our work and then move into that directory:

$ cd ~/Desktop
$ mkdir recipes
$ cd recipes

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

$ git init

It is important to note that git init will create a repository that includes subdirectories and their files—there is no need to create separate repositories nested within the recipes repository, whether subdirectories are present from the beginning or added later. Also, note that the creation of the recipes 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:

$ ls

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

$ ls -a

.	..	.git

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

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 recipes (the project we have already created), Alfredo would also like to track information about cocktails. Despite Jimmy’s concerns, Alfredo creates a cocktails project inside his recipes project with the following sequence of commands:

$ cd ~/Desktop    # return to Desktop directory
$ cd recipes      # go into recipes directory, which is already a Git repository
$ ls -a           # ensure the .git subdirectory is still present in the recipes directory
$ mkdir cocktails # make a sub-directory recipes/cocktails
$ cd cocktails    # go into cocktails subdirectory
$ git init        # make the cocktails 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 cocktails subdirectory, required for tracking files stored in the cocktails subdirectory?

Solution

No. Alfredo does not need to make the cocktails subdirectory a Git repository because the recipes repository will track all files, sub-directories, and subdirectory files under the recipes directory. Thus, in order to track all information about cocktails, Alfredo only needed to add the cocktails subdirectory to the recipes 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:

$ git status

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

Correcting git init Mistakes

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

Solution – USE WITH CAUTION!

Background

Removing files from a git repository needs to be done with caution. To remove files from the working tree and not from your working directory, use

$ rm filename

The file being removed has to be in sync with the branch head with no updates. If there are updates, the file can be removed by force by using the -f option. Similarly a directory can be removed from git using rm -r dirname or rm -rf dirname.

Solution

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

$ rm -rf cocktails/.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.