Sharing your code

Overview

Teaching: 10 min
Exercises: 10 min

Questions

• How can I share my code with others?

• What should I take into account when sharing my code?

Objectives

• Differentiate the use case for public and private repositories.

• Describe the key information that should be present in a software repository.

• Configure git with your GitHub credentials.

• Set up a repository in GitHub.

Collaborating: what you need to know?

Often, you will need to share your code with others, either with just another person in the same office or anyone, anywhere in the world. Repository hosting services let you do precisely that, keeping all the advantages of VCS and adding on top tools to ease the collaborative development of the code:

• Managing different people working on different features.
• Keeping track of the changes introduced in the code and by whom.
• Opening, reviewing, discussing and merging “pull requests”.
• Opening “issues” to report bugs, request features or discuss different aspects of the code.

GitHub: Why GitHub?

There are several widely used repository hosting services using Git, such as GitLab or Bitbucket. In this course we will use GitHub because:

• It is very easy to use and set up.
• It is, arguably, the most used hosting service of them all.
• Imperial has a GitHub Organisation any Imperial staff or student can join. You don’t need to join for this course but instructions to do so can be found here.

Set up your GitHub account

Set up your free github account:

1. Go to www.github.com/join.
2. Enter your details and click “Create an account”. You can use your Imperial e-mail address, but this is not mandatory.
3. Choose the Free plan.
4. Check your e-mail and click “Verify email address”.
5. You can fill out the questionnaire or click “skip this step”.

Create a Personal Access Token (PAT):

1. In order to access GitHub from the command line, you will need a PAT.
2. Follow the instructions here to generate one. Ensure that “repo” and “workflow” are ticked.
3. Keep the PAT safe - once you navigate away from the page you won’t be able to view it again. If you lose it, you can always regenerate it.

If you’re familiar with SSH keys, you can follow these instructions to use that alternative authentication method.

Exercise: Log in to GitHub

Check that you can log in to GitHub using your Personal Access Token, or your SSH key if you opted for that method.

If you run into any issues, ask a demonstrator for assistance so that we can all move forward together.

Private vs public repositories

Depending on who you want to give access to your repository, there are two broad types of repositories: private and public. This choice, the first one you will need to make, is not written in stone and you can set a repo private initially and make it public later on.

When you are part of an organization account, there are more options to control the visibility of a repository.

Private repositories

• Only you and the GitHub users you choose can have access to the repository.
• The repository is not listed in the GitHub directory neither it is discoverable by Google and other search engines.
• Ideal for testing, for projects with a view on commercialization, preliminary work on future open projects or for school/Msc/PhD projects not meant to be public.
• Free accounts (except if part of an Organisation account) have several limitations on the features that a private repository has (eg. fewer collaborative features, no GitHub pages, etc.).

Public repositories

• Anyone can see the repository, clone it and fork it (how it is then used depends on the license; see below).
• You keep control of who will be able to contribute to the repository.
• The choice for open source projects and to share your work to a wider potential user base.

Open Source Projects

There is a growing recognition that reproducibility and open source practices in scientific software development are closely interrelated. It is increasingly expected that publications are accompanied by the analysis code and raw data used to create them. As a budding researcher one of the best ways to improve the impact of your work is to make it as easy to reproduce as possible.

Read more:

• Open Science Massively Open Online Course
• The Turing Way
• The OpenScience Project

Things to include in your project

There are a few files that you should always include in the root directory of your repository:

README.md

• Written in Markdown, it is the front page of your repo.
• Should describe in lay terms (or not) the purpose of the software, intended audience, etc.
• Should include simplified installation instructions or a link to more detailed instructions described elsewhere.
• Often includes badges, providing quick information on the status of the documentation, the builds, the software version, license, etc.
• For inspiration see Solcore
• For further guidance see Make a README or this template.

Licence

• Important in any repository, essential in a public one.
• Describes how people are allowed to use (and reuse) the information in your repository.
• Do use a standard licence file to avoid headaches and legal issues later on.
• If your repository is part of an Organisation, make sure this organisation allows that licence. Ultimately, it will be them the ones having to fight any legal battles!!
• Licence choice is also something you should consider discussing with your supervisor if relevant, they may have strong views.

See GitHub Help: Adding a license to a repository

Licence for Imperial College London software

Imperial College’s preferred licence is the permissive BSD 2- or 3-clause. You can check the details at Imperial website: Open Source Software Licences. The guidance on this site is primarily intended for members of staff, however, it is correct for graduate students with the exception that (subject to certain conditions) you are entitled to hold the copyright. This site also tells you who you should contact in case you want a different licence model for your work e.g. commercial.

Open Source software licences

There is a huge range of different licences, ranging from fully permissive to very restrictive. A couple of websites with more information on the topic (including how to licence things that are not software) are:

• Open Source Initiative
• https://choosealicense.com

Installation process/instructions

• If short, they can be part of the README file above.
• Otherwise, they should have their own INSTALLATION.md file and, definitely, be included in any documentation you write for the software.
• Should be complete and specific for any operating system and platform you want to support.
• If you know your software will not work in, let’s say, Windows, say so!!

CITATION.cff

• Indicates how your software should be cited by anyone using it.
• A recently developed standard.
• cff = Citation File Format.
• Create and check via the provided tools.
• Supported by GitHub, Zenodo and Zotero.

Digital Object Identifiers (DOI)

If you are serious about what you are doing and want people to really cite your work properly - and get recognition for it - consider providing your repo with a digital object identifier (DOI). You can get one from:

• Zenodo
• Figshare

CONTRIBUTING.md

• Are guidelines explaining how people should contribute to your project.
• Could include steps for creating good issues or pull requests.
• Often, also have links to external documentation, mailing lists, or a code of conduct and community and behavioural expectations.

See GitHub Help: Setting guidelines for repository contributors.

Creating a repository

Now you have all the information you need to create a new repository in GitHub. Just follow these steps:

• Once logged in to GitHub, press the + symbol in the top right, and choose new repository from the dropdown menu.
• Give your repository the name example.
• Add a short description for your project.
• You are going to create a Public repository, so select that option.
• Click on Initialize this repository with a README. This will create an empty README file in the root directly that you can edit later on.
• Select a licence for your repository. Which one is up to you, but make sure you have read what they entail before (Tip: there is a little “i” next to the dropdown list with some help on this. In case of doubt, choose BSD 3 -clause.

Solution

Your repository is now ready and you should see something similar to this: It tells you there is only 1 commit, 1 branch and 1 contributor, the type of licence you have chosen and also that there are two files: LICENSE and README.md, which is also rendered immediately below.

To make this complete, let’s add some contributing guidelines:

• Go to Insights in the upper right corner of the repository.
• And then click on Community Standards on the left hand side.
• The screen now shows how the project compares with the recommended community standards. Is not bad, but could be better.
• Click on Add in the Contributing line. In the new screen you can write your contributing guidelines. Tip: No one writes this from scratch.

Have a look at some Examples of contributing guidelines and copy/paste those parts relevant for your project.

• Once you are done, click on Commit new file and the changes will be confirmed. Now you should see a CONTRIBUTING.md file in the root directory.

Key Points

• Public repositories are open to anyone to use and contribute.

• Private repositories are just for yourself or a reduced set of contributors.

• README contains a description of the software and, often, some simplified installation instructions.

• The LICENSE describes how the software must be distributed and used.

• Using one of the OSI (open source initiative) licenses is recommended if the repository is public.

• CONTRIBUTING describes how other users can help develop the software.

• CITATION helps others to cite your software in their own papers.

• GitHub can be used to set up a software repository, share your code and manage who can access it, and how.