GitHub Introduction

3 minute read

GitHub in GEN242

Note, this class will make heavy use of GitHub
Homework assignments will be submitted and graded on GitHub Classroom
Course projects will also use private GitHub repositories: one repository for each course project (shared among students of each project)
Each student will need a personal GitHub account. They can be created here.
GitHub provides an unlimited number of free public repositories to each user. Via GitHub Education students can sign up for an extended number of free private GitHub accounts (see here).
For beginners this quick guide may be useful

What are Git and GitHub?

Git is a version control system similar to SVN
GitHub is an online social coding service based on Git
Combined Git/GitHub: environment for version control and social coding

Installing Git

Install on Windows, OS X and Linux
When using it from RStudio, it needs to find the Git executable

Git Basics from Command-Line

Also try interactive git tutorial.

Finding help from command-line
```
git <command> --help
```
Initialize a directory as a Git repository
```
git init
```
Add specific files to Git repository (staging area)
```
git add myfile
```
Add all files recursively

To ignore specific files (e.g. temp files), list them in a .gitignore file in your repository’s root directory. Regular expressions are supported. See here for more details.
```
git add -A :/
```
After editing file(s) in your repos, record a snapshot of the staging area
```
git commit -am "some edits"
```

GitHub Basics from Command-Line

Generate a new remote repository on GitHub online or use hub or GitHub CLI command-line wrappers for this. To avoid errors with the online method, do not initialize the new repository with README, license, or .gitignore files. You can add these files after your project has been pushed to GitHub.
```
git remote add origin https://github.com/<user_name>/<repos_name>.git
```
Push updates to remote. Next time one can just use git push
```
git push -u origin master
```

Clone existing remote repository

git clone https://github.com/<user_name>/<repos_name>.git

Before working on project, update local git repos
```
git pull 
```

Make changes and recommit local to remote

git commit -am "some edits"; git push -u origin master

Exercise

Run the following git/github excercise from the command-line. Do this after creating a GitHub repos according to the instructions above or online as outlined here.

git clone https://github.com/<user or org>/<repo name> 
cd <repo name>
git pull
touch test # Creates empty file for testing
git add test # or use '-A' for all
git commit -am "some edits"
git push 
##-> Edit test file online and then run `git pull` to inspect changes

Online file upload

Useful for new users who want to upload their homework assignments to GitHub but are not familiar enough with the command-line yet.

Press Add file button on your repository, and then Upload files.
Under the file path window add required subdirectory structure and a dummy file name (e.g. Homework/HW1/dummy.txt)
After this press Upload files and upload any file (e.g. homework) to the newly create directory. After this the initial dummy file can be deleted. The latter is necessary since empty directories are not visible on GitHub.

Using GitHub from RStudio

After installing Git (see here), set path to Git executable in Rstudio:
- Tools > Global Options > Git/SVN
If needed, log in to GitHub account and create repository. Use option Initialize this repository with a README.
Clone repository by copying & pasting URL from repository into RStudio’s ‘Clone Git Repository’ window:
- File > New Project > Version Control > Git > Provide URL
Now do some work (e.g. add an R script), commit and push changes as follows:
- Tools > Version Control > Commit
Check files in staging area and press Commit Button
To commit changes to GitHub, press Push Button
Shortcuts to automate above routines are here
To resolve password issues, follow instructions here.

Last modified 2021-04-01: some edits (cbcc639fc)