Version control with Git

Setting your Git environment

On a terminal, specify the email address with which you will make your commits:

$ git config --global user.email "prenom.nom@domaine.fr"

Of course Adapt the email address prenom.nom@domaine.fr to your case!.

You may also (optional) configure another option (yet mysterious):

$ git config --global pull.rebase false

Create an SSH key

Unix system

The SSH is needed to get a smooth authentication to the remote repository. In a terminal:

$ ssh-keygen -t rsa -b 4096 -C prenom.nom@domaine.fr

Accept the default option (keys saved in ~/.ssh and no passphrase):

ssh-add

Reference: Github docs on connecting with SSH.

Windows

Reference: The Server Side: How to SSH into GitHub on Windows example, by Cameron McKenzie

Setting up your GitHub account

GitHub is a web hosting service for remote repositories using git. GitHub includes additional features for collaboration, such as bug tracking, requests to add features or task management.

Note that there are other git-based hosting websites such as GitLab or BitBucket.

Create a GitHub account

Please go to Github and follow the instructions for creating or activating your account.

Add your SSH key

To display your public key, simply type in a terminal:

$ cat ~/.ssh/id_rsa.pub

Copy the result into the clipboard and add your key to your GitHub account, following the procedure explained on GitHub here.

To check your installation, please follow the instructions given on GitHub here.

Create a remote repository

Let us create a remote repository hosted on your GitHub account.

On GitHub, click on the + symbol at the top right of the page, then New repository. Give the name FirstRepo to your new project and a short description.

Create a public repository, meaning that everyone can access your code (read-only). Finish by clicking on Create repository.

Follow the instructions provided by GitHub to create your local copy of the repository:

  1. Create a new folder called FirstRepo in your home directory and cd to it.

  2. Then execute the following command changing the XXXXXXXXXXX with the relevent URL.

    echo "# FirstRepo" >> README.md
git init
git add README.md
git commit -m "first commit"
git branch -M main
git remote add origin git@github.com:XXXXXXXXXXXXXXXXXX/FirstRepo.git
git push --set-upstream  origin main
EXERCISE: gitignore
  1. Create a text file called .gitignore with the following content:
*.pdf
*~
  1. Create a commit and push it to your repository. What is the purpose of this file? See https://github.com/github/gitignore.

Interact with other users

The purpose of this exercise is to learn how to use git as a collaboration tool for software development.

Using an existing repository

Browse the repository at https://github.com/bcharlier/HAX712X_2023. What is this module able to do?

EXERCISE: Forking a Git repo

Fork the repository by following these steps:

  1. On GitHub, click on the fork icon.
  2. A copy is added to your GitHub space. Clone it (this copy!) to get a local repository.
  3. In a terminal, inspect the output of the command git remote get-url origin.

Debugging

A bug has appeared in the Python module after a commit. An issue has been opened in the bug tracking system at https://github.com/bcharlier/HAX712X_2023/issues/. Your goal is to find the problem… and then fix it on your forked repository. Finally, you will be able to submit a Pull Request to the original repository to share your fix.

Identification of the bad commit

Your goal is to identify the commit(s) that caused the bug. Use git log, git diff, git checkout to identify the commit responsible for the problem.

Reference: Git Bisect

Create a new branch to fix the problem

To fix a complex bug or add a new feature, it is often necessary to modify several parts of the code. We create a branch, where we make all the commits dedicated to solving the bug. The idea is to maintain a stable version, in the branch main, separated from the developing version, which may contain bugs.

EXERCISE: branches
  1. Create a local branch Fix_EOL_Error.
  2. Push this local branch to your remote repo.
  3. Switch to the Fix_EOL_Error branch, and fix the bugs. The branch main will not be affected.
  4. Merge the fix into the branch main.
  5. Delete the local branch Fix_EOL_Error and the remote origin/Fix_EOL_Error branch.

Pull request

Your work about bug fixing may interest the original author of the project. On GitHub, open a pull request (PR). PRs are a set of commits that can be integrated directly by the author of the project in its repository and are thus a powerful tool for working with others.

Branch Merging and Solving conflicts

EXERCISE: Conflicts identification
  1. Switch to the branch NonGaussian. Try to figure out what has changed compared to the main branch.
  2. Try to merge the branch NonGaussian to the branch main.
  3. Where are located the conflicts? They are shown with the following decorator.
<<<<<<< HEAD
Some code on the current branch
=======

Some code on the branch to be merged
>>>>>>> NonGaussian
  1. Resolve them by plotting the two histograms on the same plot. Namely, produce a figure like this:plot

References

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