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 digits-classifier
$ cd digits-classifier

Then we tell Git to make digits-classifier 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 digits-classifier 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 master

Initial commit

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

Places to Create Git Repositories

Bob starts a new project to work on a Support Vector Machine, svm, for his digits-classifier project. Despite Alice’s concerns, he enters the following sequence of commands to create one Git repository inside another:

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

Why is it a bad idea to do this? (Notice here that the digits-classifier project is now also tracking the entire svm repository.) How can Bob 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 recover from this little mistake, Bob can just remove the .git folder in the svm subdirectory. To do so he can run the following command from inside the digits-classifier directory:

$ rm -rf svm/.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.

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:

$ touch svm/classify.py         # create svm files
$ cd ..                         # return to digits-classifier directory
$ ls svm                        # list contents of the svm directory
$ git add svm/*                 # add all contents of digits-classifier/svm
$ git status                    # show svm files in staging area
$ git commit -m "add svm files" # commit digits-classifier/svm to digits-classifier Git repository

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

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

svm

Key Points

• git init initializes a repository.