Git and GitHub

Luke Marsden, UNIS

(data.nleg@unis.no)

What is version control and why use it?

• Both can add to or remove things from list
• Don’t override each others changes
• Track who has added what
• Both work on list at same time
• Revert to old versions

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Why use GitHub?

• Both can edit from their own offices
• Adam can also use the list
• Adam can chip in with suggestions
• Adam’s suggestions must be approved by Max or Tom

*Adam could be anyone

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Adam

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Downloading Git

https://git-scm.com/downloads

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Using Git Bash

Create repository

1. From GitHub

Create repository

• Create local directory and navigate into it in your terminal
• Clone the git repo in your local directory. Copy & paste URL of repo. Paste is middle mouse button in Git Bash.
• Navigate into repository.

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1. From GitHub

Create repository

2. Locally and

upload

• Create local directory and files (or maybe you already have one you want to use).
• Create empty GitHub repository (as previous)
• Initialise the directory as a git repository
• Add the files to be committed
• Commit the files that you have staged
• Link repo to ‘remote’ repo at GitHub
• Push repo to GitHub

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Create repository

2. Locally and

upload

Commits

• Commit is a snapshot of repository
• Repo contents, author, timestamp…

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C0

Added pizza to shopping list

main*

Initial commit

Pushing

• Local main branch ahead of remote master branch (on GitHub)

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C0

local main*

remote main

ID of commit

ID of parent commit

Branch name

Making changes on GitHub

Pulling

• Update local repo with remote changes
• ‘pull’ the latest version from GitHub.
• Pull often for updates

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C0

local main*

remote main

Branches

C0

main*

newBranch

• Branch is pointer to a commit
• New branch to work outside of main work flow – common practice if multiple users
• Checkout new branch
• Can create new branch and checkout 1 line

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main

newBranch*

Merging branches

• Working on newBranch, updated file and committed changes.
• Checkout branch you want to merge into
• Merge newBranch so changes on main
• Delete branch if no longer needed
• Push changes

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C0

main

newBranch*

main*

newBranch

Two people working at same time

• Two people checkout new branches
• Both branches have new commits
• Checkout main and merge newBranch1
• Try merge newBranch2, conflicts with main
• git status, git log can help, then open file
• Fix conflicts then add and commit

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C0

main*

newBranch1*

newBranch2*

main

newBranch1*

newBranch2*

main

newBranch1*

main

main

newBranch2*

newBranch1

main*

From newBranch2

From main (HEAD denotes current branch)

Common to both

main

newBranch2

Diff

• Forgot what changes you’ve made
• Check changes made since last commit

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Pull requests

• Best practice for documenting and reviewing changes
• Pull, create new branch
• Make changes, add, commit
• Push – new branch appears on GitHub

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C0

local main*

main

main

newBranch*

local

remote

main

newBranch*

newBranch

Pull requests

• Best practice for documenting and reviewing changes
• Pull, create new branch
• Make changes, add, commit
• Push – new branch appears on GitHub
• Create pull request – to merge branches
• Someone else reviews pull request

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Forks and pull requests

• Working on a repo that isn’t yours.
• Forking creates copy of repo.
• Clone forked repo in git bash.
• Checkout a new branch.
• Make, add, commit and push changes.

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Forks and pull requests

• Working on a repo that isn’t yours.
• Forking creates copy of repo.
• Clone forked repo in git bash.
• Checkout a new branch.
• Make, add, commit and push changes.
• Go to GitHub, fork repo, submit pull request
• Owner of parent repo reviews pull request.

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What to include in a README

• Project name

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• Short description of project

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• Contents of repository with descriptions

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• Instructions on how to install and use your scripts/software

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• Credits – who is involved?

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Final remarks

Pull from origin (GitHub) before you start to update your local repository.

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Push and pull regularly, especially if multiple users of repository.

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Don’t work on main branch, create new one then merge or submit pull request.

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This is just an introduction

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There is SO much help online

• Stack Overflow
• Youtube (e.g. this playlist by ‘The Net Ninja’)
• Google

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My favourite visual, interactive way to learn git branching and version control:

• https://learngitbranching.js.org/