Introduction to Git and GitHub

class: center, middle, inverse, title-slide

# Introduction to Git and GitHub
### Computation Skills Workshop

---

# Why Git?

.footnote[Source: [Excuse Me, Do You Have a Moment to Talk About Version Control?](https://www.tandfonline.com/doi/full/10.1080/00031305.2017.1399928)]

- Version control system
- Repository

---

# Why GitHub?

.footnote[Source: [GitHub](https://www.github.com)]

---

# Why bother?

.pull-left[

## Will it hurt?

**Yes** 🤷

- More complicated workflow
- Clunky at first
- Need to break bad habits

## What's the payoff?

- Ease of access
- Collaboration

]

.pull-right[

]

---

# Install Git

```bash
which git
## /usr/bin/git
```

- [Install Git](https://git-scm.com/)

---

# ⏱ Configure Git

.pull-left[

## `usethis`

```r
# install.packages("usethis")

library(usethis)
use_git_config(
  user.name = "Jane Doe",
  user.email = "jane@example.org"
)
```

```r
# default branch named 'main'
git_default_branch_configure()
```

]

.pull-right[

## From the shell

```bash
git config --global user.name 'Jane Doe'
git config --global user.email 'jane@example.com'

git config --global init.defaultBranch main
```

]

---

# ⏱ Create a local Git repo

- Run `usethis::use_course("css-skills/practice-repo")` in the console
- Create Git repo with `use_git()`
- Practice generating **commits**

---

# 🔑 Key terms

- Stage
- Commit
- Push

---

# `.gitignore`

```r
usethis::edit_git_ignore(scope = "project")
```

---

# Connect RStudio and GitHub

- Interacting with GitHub
- Providing **credentials**

- Personal access token (PAT)

---

# ⏱ Painless authentication with PAT

```r
usethis::create_github_token()
```

```r
gitcreds::gitcreds_set()

#> ? Enter password or token: ghp_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
#> -> Adding new credentials...
#> -> Removing credentials from cache...
#> -> Done.
```

---

# ⏱ Connect project to GitHub

.pull-left[

```r
usethis::use_github()
```

]

.pull-right[

]

---

# Get a sitrep

```r
usethis::git_sitrep()
```

---

# ⏱ New project, GitHub first

- Create a Git controlled project already connected to GitHub

1. Make a repo on GitHub
1. New RStudio Project via `git clone`
1. Copy files from the first project to the new project
    - Stage
    - Commit
    - Push

---

# ⏱ Incorporating changes from GitHub

1. Make a change on GitHub and commit
1. **Pull** changes from GitHub locally

---

# Git for collaboration

.footnote[Source: [Excuse Me, Do You Have a Moment to Talk About Version Control?](https://www.tandfonline.com/doi/full/10.1080/00031305.2017.1399928)]

---

# Git for collaboration

.footnote[Source: [Excuse Me, Do You Have a Moment to Talk About Version Control?](https://www.tandfonline.com/doi/full/10.1080/00031305.2017.1399928)]

---

# Branching

.footnote[Source: [Bitbucket tutorials](https://www.atlassian.com/git/tutorials/using-branches)]

---

# ⏱ Create a branch

1. Create a branch using RStudio
1. Modify a file in the repo
1. Stage, commit, and push to GitHub
1. Check the repo on GitHub -- what has changed?

---

# Merging branches

.footnote[Source: [Bitbucket tutorials](https://www.atlassian.com/git/tutorials/using-branches)]

```bash
git checkout main
git merge BRANCH-NAME
```

---

# Merge conflicts

---

# Merge conflicts

```bash
git merge documentation
# Auto-merging README.md
# CONFLICT (content): Merge conflict in README.md
# Automatic merge failed; fix conflicts and then commit the result.
```

```bash
<<<<<<< HEAD:README.md
Contact: ben@bensoltoff.com
=======
Please contact me at ben@bensoltoff.com
>>>>>>> documentation:README.md
```

- Resolving merge conflicts

---

# ⏱ Practice a merge conflict

- Generate distinct changes in the README file
    - One form locally
    - Another form on GitHub
- Attempt to push to GitHub
- Pull from GitHub, resolve merge conflicts
- Stage, commit, and push

---

# Pull requests

---

# Pull requests

- Inform others about changes you've pushed
- Discuss and review potential changes with collaborators
- Easily add follow-up commits before changes are merged

---

# ⏱ Create a pull request

1. Open a pull request from your new branch
1. Merge the pull request on GitHub
1. Pull the revised `main` branch to your local repo

---

# Forking

---

# Forking

.footnote[Source: [Happy Git with R](https://happygitwithr.com/fork-and-clone.html)]

---

# Forking

```r
usethis::create_from_github("OWNER/REPO")
```

- Or interactively on GitHub

---

# ⏱ Forking

1. Create a fork of [`css-skills/practice-repo`](https://github.com/css-skills/practice-repo)
1. Stage, commit, push a change to GitHub
1. Open a pull request to the original repo

---

# Other useful GitHub features

- Issues
- Private repos
- [Free GitHub Pro while you are a student](https://education.github.com/discount_requests/student_application)

---

# Other useful `usethis` functions

- [Pull request helpers](https://usethis.r-lib.org/articles/pr-functions.html)
- [All the `usethis` git functions](https://usethis.r-lib.org/reference/index.html#git-and-github)

---

# Don't use RStudio much?

Not required for Git!

- Pick a [Git client](https://git-scm.com/downloads/guis) (or do it all in the shell!)
- Check if your IDE has Git integration
- Use a [project-oriented workflow](https://rstats.wtf/project-oriented-workflow.html)

---

# When in doubt...

.footnote[Source: [xkcd](https://xkcd.com/1597/)]