Copy and browse an existing project

Objectives

We will fork the example project.
We will find a point in history when a code default changed (using git annotate).
We will create a branch and a commit with a new file added to exercise directory.

Repositories and branches

What is a Git repository?

Git repository contains a bunch of files and tracks their changes over time.
Git repositories typically reside on GitHub or GitLab or on your computer or on some server.
Git repositories track changes using commits.

What are branches?

Commits form a history of changes and the history can be visualized as a tree which contains branches.
Each repository has a default branch. It is often called main or master.
Branches are like parallel universes where you can experiment with changes without affecting the default branch.
Browse the network of branches in our example repository (“Insights” -> “Network”): https://github.com/coderefinery/imgfilters/network

Annotated history

Let us try the annotation feature (“git blame”)

The function gaussian_smoothing has a default value for sigma. But this default used to be different.
Find out when this default value was changed (which commit).
Would you be able to do this archaeology work with your project?
Is the commit message informative about why this was changed?

What is a fork? Let’s create and browse it!

A fork is a full copy of a repository.
You have then write permissions to your copy.
Once a fork is created, you decide when to sync changes from the original repository - it does not happen automatically.

Exercise/demo: creating a new branch and a new commit

You can try this or you watch the instructor doing it.

Creating a new branch and a new commit

Create a new branch in your fork and give it a descriptive name.
Add a new file in the exercise directory to the new branch.
In this file we will try to answer: “What do you know now about programming that you wish you knew when you started?”.
The new branch and new file now only exist on the fork, not yet in the original repository.

How does this relate to your own work?

Summary

Forking is useful if you want to modify a repository that you do not have write access to or if you want to allow others to experiment with your repository.
Within your research project you probably want to give all project members write access and then you can work within the same repository.
If you are more than 1 person working on a project, it can be useful to make the main branch protected and to always create a new branch for each new feature or bug-fix or idea.
In the next episode (Collaboration and code review using issues and pull requests) we will discuss how to suggest changes from a fork or within the same repository.

More resources

In this short workshop we focus on what is possible and what are good practices but we cannot focus on how to do these in detail across the many user interfaces (GitHub web, GitLab web, command line, VS Code, other editors).

Here we go through those in detail: Introduction to version control with Git