A short introduction to Git

# Computational Science Seminar

### A short introduction to version control with Git

Will Usher, Tom Russell & Roald Lemmen

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# Agenda

1. intro
1. concepts
1. live coding
1. summary
1. next steps

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## Resources

These slides are available from:
- https://nismod.github.io/presentations/a-short-intro-to-git.html

Further resources are available from the website:
- https://nismod.github.io/git-novice/

A list of commands used in the session is available for quick reference:
- https://nismod.github.io/git-novice/commands/

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## Introduction

* Given the limited time we can only give you a flavour of version control

* This session will provide a bit of theory and a bit of practical demonstration

* A more detailed practical will be scheduled for next term

* Version control (and git in particular) has a steep learning curve – do ask
  for help getting started

* There are many resources for self learning
  * Software Carpentry
  * Courses within the University of Oxford
  * The Research Support team in SOGE

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## Motivation!

![Climbing with a rope](../fig/git-climbing-rope.png)

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## Motivations

- Ability to move back, try things out, 'unlimited undo'
- Log of changes to code
- Working together, not accidentally overwriting
- There is only one 'latest' version
- Remote backup (in the cloud)

Opportunities

- Publishing code in citeable form
- Open-source integration with testing, code quality, documentation

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## Concepts

- **repository**

a place for a project

- **commit**

a small set of changes, which accumulate to make a **history** of commits

- **remote** repository

a place to share a project (Gitlab, Github)

- **branch**

a way to separate work on new versions, bug-fixes or features

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## Commits

![Changes Are Saved Sequentially](../fig/play-changes.svg)

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## Repository

![Commit changes to a repository](../fig/git-repository.svg)

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## Remote

![Remote Repository After Creation](../fig/git-remote.svg)

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## Remote

![Remote Repository After remote-add](../fig/git-remote.1.svg)

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## Remote

![Remote Repository After First Push](../fig/git-remote.2.svg)

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## Branch

![Different Versions Can be Saved](../fig/versions.svg)

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## Merge

![Multiple Versions Can be Merged](../fig/merge.svg)

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## Collaborating with git

![Github flow](../fig/github-flow.png)

[https://guides.github.com/introduction/flow/](https://guides.github.com/introduction/flow/)

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## Live coding in progress

![Kermit typing](../assets/img/typing-kermit.gif)

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## Summary

Starting out

`git init`

`git clone`

<br>

Committing

`git add ...`

`git commit -m "..."`

<br>

Information

`git status`

`git log`

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## Summary

Remotes

`git push`

`git pull`

<br>

Branches

`git branch ...`

`git merge ...`

`git checkout ...`

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## Git Documentation

`git --help`
<br>

Git manual
- https://git-scm.com/docs/git

Git book
- https://git-scm.com/book/en/v2

Cheatsheet from Github
- https://education.github.com/git-cheat-sheet-education.pdf

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## Thanks!

Questions?

[https://nismod.github.io/presentations/a-short-intro-to-git.html](https://nismod.github.io/presentations/a-short-intro-to-git.html)

tom.russell@ouce.ox.ac.uk

roald.lemmen@ouce.ox.ac.uk