Collaboration

Discussion

Menti

Have you downloaded programs/tools from GitHub?
Have you uploaded your own programs/tools and believe that people are using your tool?

Objectives

We will give an overview GitHub
- centralized collaboration
- Forked collaboration
- How to contribute
You will test this more later this week so we won’t get deep

Instructor note

Different types of remotes

If you have a server you can ssh to, you can use that as a remote.
GitHub is a popular, closed-source commercial site.
GitLab is a popular, open-core commercial site. Many universities have their own private GitLab servers set up.
Bitbucket is yet another popular commercial site.
Another option is NotABug

GitHub

There are two more ways to create “copies” of repositories into your user space:

A repository can be marked as template and new repositories can be generated from it, like using a cookie-cutter. The newly created repository will start with a new history, only one commit, and not inherit the history of the template.
You can import a repository from another hosting service or web address. This will preserve the history of the imported project.

Cheat-sheet

Commits, branches, repositories, forks, clones

repository: The project, contains all data and history (commits, branches, tags).
commit: Snapshot of the project, gets a unique identifier (e.g. c7f0e8bfc718be04525847fc7ac237f470add76e).
branch: Independent development line, often we call the main development line master or main.
tag: A pointer to one commit, to be able to refer to it later. Like a commemorative plaque that you attach to a particular commit (e.g. phd-printed or paper-submitted).
cloning: Copying the whole repository to your laptop - the first time.
- It is not necessary to download each file one by one.
- good within a group
forking: Taking a copy of a repository (which is typically not yours)
- your copy (fork) stays on GitHub and you can make changes to your copy.
- better for contribution to other’s project
git clone copies everything: all commits and all branches.
Branches on the remote appear as (read-only) local branches with a prefix, e.g. origin/master.
We synchronize commits between local and remote with git fetch/git pull and git push.
Repositories that are shared online often synchronize via pull requests or merge requests.
Repositories that are forked or cloned do not automatically synchronize themselves.

Centralized workflow

**Centralized layout**

**Red** is the repository on GitHub.

**Blue** is where all contributors work on their own computers.

Centralized workflow is often used for remote collaborative work.
origin refers to where you cloned from (but you can relocate it).
origin/mybranch is a read-only pointer to branch mybranch on origin.
These read-only pointers only move when you git fetch/git pull or git push.

Distributed version control and Forking workflow

In the forking layout described above we work with multiple remotes, in this case two remotes: One remote refers to the “central” repository, and the other remote refers to the “fork”.

Working with multiple remotes is not as scary as it might look.
origin is just an alias/placeholder.
We can add and remove remotes.
We can call these aliases/placeholders as we like.
We typically synchronize/updates remotes via the local clone.
To see all remotes use git remote -v.
If you are more than one person contributing to a project, consider using code review.

How to contribute changes to somebody else’s project

Avoid frustration and surprises by first discussing and then coding.

Contributing very minor changes

Fork repository
Create a branch (e.g. with your name)
Commit and push change
File a pull request or merge request

If you observe an issue and have an idea how to fix it

Open an issue in the repository you wish to contribute to
Describe the problem
If you have a suggestion on how to fix it, describe your suggestion
Possibly discuss and get feedback
If you are working on the fix, indicate it in the issue so that others know that somebody is working on it and who is working on it
Submit your fix as pull request or merge request which references/closes the issue

(Optional) Add to someone else’s project

You can from the breakout room group decide on some collaboration if you want to!

Make issue and pull requests
Remember that we were not happy with the results
Can we easily add one or more planets?
The importance of each planet should be determined by the distance and the mass of it.
- The acceleration effect should proportional with MASS/distance^2
- That means that we can ignore small planets and/or far away planets
Below, see a first sorted out table of mass of the planets and their approximate shortest distance to Earth.

Planet	Mass (relative to Earth)	Mean distance to sun (AU)	Shortest distance to earth (AU)
Venus	0.815	0.72	0.28
March	0.107	1.52	0.52
Jupiter	318	5.2	4.2
Saturn	95.2	9.54	8.54

Adding a planet should be pretty straight-forward in our modular code!
For ideas view Code Refinery’s Centralized workflow