git-tutorial.Rmd

---
title: "Using Git and GitHub"
subtitle: "A Gentle Introduction"
date: '`r format(Sys.Date(), "%d %B %Y")`'
footer: "An Gentle Introduction to Using Git and GitHub"
output: 
  slidy_presentation:
    smart: no
    fig_caption: yes
graphics: yes
---

# Overview

```{r setup, echo=FALSE}
knitr::opts_chunk$set(echo = FALSE)
shiny::includeCSS("css/slidy-flatly.css")
shiny::includeScript("js/jquery.min.js")
shiny::includeScript("js/jkf-scroll.js")
```

## This presentation answers the following questions

- What are Git and GitHub?
- What are version control systems?
- Why should someone use a version control system?
- What is a centralized version control system (CVCS)?
- What is a decentralized (aka distributed) version control system (DVCS)?
- How do I install and configure Git?
- What are the main Git commands and what do these commands do?
- What's inside the `.git` directory?
- What are the different ways to interact with Git?
- What is a Git remote and how do I add one to a repo?  
- How do I get started with Github?


- How do I get started using Git and Github?

    + From the command line
    + Within the RStudio IDE 

# Overview of Git & Github

## What is Git?

- A <u>decentralized<u/> version control system that's free and open source

- An excellent way to track and coordinate file changes among many people

- A tool invented by Linus Torvalds (and the Linux development community) to develop the Linux kernel in 2005

## Is Git hard to learn?

- New Git users often struggle to understand how to use Git?

- This misunderstanding is driven by the fact that there seems to be an endless number of use cases

- Git's not hard to learn -   
    + There are problem 

- Before 

## What's a decentralized version control system?



<center>
<img src="Git.png" style="width: 400px; background-color: black;">
</center>

# What is GitHub?

- A web-based service for hosting Git repositories

- The single largest host for Git repositories

- A popular way to collaborate on code (no more emails and zip files!!)

    + The development versions of many R packages are hosted on GitHub: https://github.com/tidyverse/ggplot2
    + All the [cool kids](https://github.com/auburngrads) are using it!

<!--## 
    + what is Git?
    + Installing Git on your machine
    + basic commands
    + setting up a Git repo on a local machine

- GitHub

    - what is GitHub?
    - signing up
    - connecting your local Git repo to GitHub
    - selecting an awesome avatar will not be covered

# Git
-->

## Why Should You use Git/GitHub?

## Git enables a faster, easier workflow

<img src="before-version-control.png" style="float: right; padding: 0px 0px 0px 5px; width:250px;">

<ul style="display:inherit;">
- A typical workflow

    * File renaming
    * Absurd folder structures
    * Zipped folders
    * E-mailing files back and forth
    * Lost files
    * Shared directories (one-at-a-time)
    * Ever try merging MS Word files with tracked changes?!
</ul>

## Your workflow - <font color='red'><u>without</u></font> Git

<center>![](giphy-frustrated.gif)</center>

## Your workflow - <font color='green'><u>with</u></font> Git

<center>![](images/giphy-thumbsup.gif)</center>

## Using Git

## Using Git

- There several Methods for using Git 

    - At the **command line**
    - Within an IDE (e.g. RStudio)
    - From one of several [Git desktop GUI](https://git-scm.com/downloads/guis)
    - <p class='hover'>Super secret hybrid method</p>

## Which method should you choose?

- At the **command line**

    + Simplest (really!) & fastest
    + Works the same on Windows, Mac, and Linux
    
- Within an IDE (e.g. RStudio)

    + Convenient when building R packages
    + Can be clunky to update many files
    
- From a Git [desktop GUI](https://git-scm.com/downloads/guis)

## Installing Git

## Installing Git (Mac/linux/unix)

- For Mac, Linux, and Unix users

    + Download Git from https://git-scm.com/downloads. 
    + Accept the installation defaults for your particular operating system

## Installing Git (windows)

- For Windows users

    + Download Git from https://git-scm.com/downloads. 
    + Accept the installation defaults __EXCEPT__ Choose Use Git Bash

<img src="images/win-git.png" width='50%' style="border: 0px; box-shadow: 0;">

## Setting Git up for the first time

- After Git has installed

    + You need modify the global configuration file to tell Git who you are.
    + Open a terminal or Git Bash (Windows) and enter the following two lines: (with the obvious modifications) 
    
```{shell, echo=TRUE}
$ git config --global user.name "Brandon Greenwell"
$ git config --global user.email greenwell.brandon@gmail.com
```

- Since you passed the option `--global`, you only need to do this once!

## The basic process

- Initialize Git version tracking in a directory
- Add or edit files in the directory
- Check the status of file changes in the directory
- Add changed files to the staging area
- Commit one or changed files to be updated
- Push commits to the master

## The basic commands you'll use/need

- `cd` (change directories)
- `git init` (initialize a folder as a Git repo)
- `git add <file-name>` (start tracking a new file)
- `git commit -m "fix typo"` (commit your changes)
- `git clone` (clone/copy another Git repo [e.g., from GitHub])
- `git push origin master` (push your master branch to your origin server)
- `git pull origin master` (update your local repo)
**Tip\:** Typing `git add --all` will start tracking everything (this is how I almost always use `git add`).

## Using Git commands

- Initialize a repo in an existing directory

    + Create a new folder called `arithmetic` anywhere on your computer (e.g., the Desktop) 
    + In this folder, create a new R script file called `add.R` 
    + In this new file add the following code
    
```{r, echo=TRUE}
add <- function(x, y) { x * y }
```

## Initializing a repo in an existing directory

- Next, open a terminal or Git Bash (Windows) and go to the project's root directory

- For example, the code below takes me to the folder called `arithmetic` on my Desktop

```{shell, echo=TRUE}
cd C:/Users/greenweb/Desktop/arithmetic
```

- Then, to initialize this as a Git repo, just type
```{shell, echo=T}
git init
```

**Tip\:** the command line has a history (just like the R console), so you don't need to type as often; just hit the up arrow and make any necessary changes!


## Initializing a repo in an existing directory

If you want to start version controlling all the files, you need to start tracking them. In the terminal, type the following:
```shell
git add --all
```
then type:
```shell
git commit -m "first commit"
```

## How to use Git

* Free book on the Git website: https://git-scm.com/book/en/v2

```{r, out.width = "150px"}
knitr::include_graphics("progit2.png")
```


# GitHub

```{r, out.width = "600px"}
knitr::include_graphics("Octocat.png")
```



## Account setup and configuration

The first thing you need to do is set up an account: https://github.com/

```{r, out.width = "400px"}
knitr::include_graphics("signup.png")
```

**Use the same e-mail address you used when setting up Git!**


## Set up your profile

```{r, out.width = "700px"}
knitr::include_graphics("my-profile.png")
```


## Creating a new repo

```{r, out.width = "600px"}
knitr::include_graphics("new-repo.png")
```


## Creating a new repo

```{r, out.width = "600px"}
knitr::include_graphics("new-repo-2.png")
```


## Creating a new repo

```{r, out.width = "700px"}
knitr::include_graphics("new-repo-3.png")
```


## Creating a new repo

```{r, out.width = "700px"}
knitr::include_graphics("new-repo-4.png")
```


## Creating a new repo

Refresh your browswer and see if it worked!

```{r, out.width = "700px"}
knitr::include_graphics("new-repo-5.png")
```


## Making changes and pushing them to GitHub

Fix the obvious typo in `add.R`. Then, take a snapshot (i.e., `git add/commit`) and push the changes to GitHub (i.e., `git push`)!
```shell
git add --all
git commit -m "fix typo"
git push origin master
```
Refresh your browser to see the changes.

**Tip\:** It's good practice to do this every time you make a key change (e.g., fix a typo, add a new function to an R script, etc.).

\* Make sure you're in the right directory!


## All done!

<center>![](giphy-shaun.gif)</center>

**Any questions?**