Git is a free and open source distributed version control system designed to handle everything from small to very large projects with speed and efficiency.

Learn Git

`git pull` lets us get the latest changes from our project's remote repo (most likely from co-workers or other developers working on our project) and merge (combine) them with our local code. It's kind of like Dropbox for code, but you tell git when you want it to get the latest changes from the remote when it is most convenient for you. In this lesson, we use `git pull` and discuss how it is a shortcut for running `git fetch` and `git merge`.

Practical Git: Sync local and remote repos with git pull

When working on a project, it is much easier to work on features and bugs in isolation of the rest of the project. We can do this with git branches; a branch is a copy of the working directory, staging area, and project history; we create a branch, then check it out, then add commits. After our feature has been built, we can then merge it back into the main stable branch - which is `master` by default. In this lesson we go over how to create a branch with `git branch {branch-name}`, viewing all branches with `git branch`, switching branches with `git checkout` plus a few helper commands.

Practical Git: Isolate feature development with git branch

Getting started with Git requires you to add a .git folder to your project on your machine and then set up that folder to point to a remote repository. In this lesson, we walk through using `git init` and `git remote` to do this; we use GitHub for this remote repository as an example, but keep in mind that any Git repo hosting service will work.

Practical Git: Create local repos with git init

When working on code, we need a way to stay in sync across multiple devices and potentially multilpe team members. We also may need to work on our code offline. To do these things, we can "clone" a remote repo (from a git repo hosting service like GitHub or Bitbucket); git cloning means we make a copy of an existing remote repository onto our local machine with the `git clone` command. This command also automatically sets up the remote repo and branch tracking. Once our repo is cloned to our machine, we can work on the code in this directory offline or with teammates at the same time and then when we need to sync up we can push our code back to the central “remote" repo; we can also clone this same repo onto multiple machines and “pull” updates from the central “remote" repo whenever we want. In this lesson, we walk through how to do this.

Practical Git: Copy remote repos to local machines with git clone

Sometimes when you run `git merge` (also during a `git pull` which runs a `git merge`) you get a merge "conflict"; this means that the same line(s) of code were changed locally as in new changes in the remote (most likely from another developer working on a related feature); `git merge` can automatically merge all other changes but when the same line is modified in two places, you have to fix the conflict manually. In this lesson, we show how a conflict happening from a `git pull`, and then how to fix it using `git status` to update the conflict markers in our file(s) with conflicts. You can use a graphical app for this, but this lesson will show you how to resolve conflicts directly from the command line and your code editor.

Practical Git: Resolve merge conflicts with git status

Once a feature has been created inside of a branch, we can combine it back into the main `master` branch by using `git merge`. In this lesson, we go through a complete workflow of creating a feature branch and merging it back into the `master` branch.

Practical Git: Sync branches with git merge

Sometimes when we are working we need a way to pause and switch gears to deal with something more critical; often when this happens we aren't ready to create a `git commit`; instead, we can use `git stash` to save our uncommitted changes locally, switch branches and fix the critical issue, switch back to our incomplete feature, and finally run `git stash apply` to get our unfinished changes back into our branch without affecting the rest of the codebase. In this lesson, we show a real world example of doing this with a critical bug.

Practical Git: Save uncommitted changes with git stash

In this lesson we’ll talk about what GitHub is and how to sign up for a GitHub account so you can contribute to an open source project on GitHub.

Introduction to GitHub

GitHub adds a lot of great features on top of git repository hosting. We’ll take a look at some of these features including:

- How to create a repository and organization on GitHub
- How to explore and find projects on GitHub
- About GitHub gists
- Searching pull requests and issues on GitHub

Exploring GitHub

The basic unit of GitHub is a repository. This is where your code is stored and GitHub allows you to interact with others and with the code in great ways. In this lesson we talk about Watching, Starting, and Forking a repository. We also cover GitHub issues and pull requests and various other stats about a GitHub repository.

Exploring a Repository

Let’s install the Git Source Control Management software so we can interact with repositories hosted on GitHub.

How to install Git SCM

If you regularly use code editors, GUI tools or other programs that automatically create files and folders, you may want to set up a global `.gitignore` file which will apply to every repo on your machine. In this lesson, we show how to do that by creating a `.gitignore_global` file with the dotfiles in our `~/` root directory, and then link it to all git repos using our global `.gitconfig`.

Practical Git: Remove all unnecessary git tracking with a global .gitignore file

Anytime you push code to GitHub, you must be authenticated so GitHub knows you are authorized to make changes. In this lesson we’ll learn how to authenticate with GitHub using SSH so we don’t have to enter our username and password each time we push code to GitHub.

How to authenticate with GitHub using SSH

It's often helpful to view the history of a code project; with Git, we can use the `git log` command to view all commits in our repo. This lets us view information about each commit like the commit id (for use in other git commands), author, author's email, and commit message. We can format the git log commit output to display more or less information or filter to specific commits using `git log {arguments}` which will be covered in the next few lessons of the course.

Practical Git: View commit history with git log

When using a git command that can have a large amount of output (like `git log`, `git diff`, or `git blame`), Git opens the command output in our terminal "pager"; on most modern Unix-based systems, the default pager will be ["less"](https://en.wikipedia.org/wiki/Less_(Unix)). Learning a few _less_ commands will help us deal with this git command output that opens in the pager. In this lesson, we show some of the most useful of the less commands: `q` (quit), `j` (down), `k` (up), `Ctrl f` (forward), `Ctrl b` (backward), `/{search}` (search), and `n`/`N` (next/previous search result).

This lesson only covers some of the most critical _less_ commands; there are more commands available. A good chunk of the commands (and "motions") of the Unix pagers are also used by vi (or vim) and other Unix programs.

Practical Git: Navigate git command pager output with Unix less commands

In the last lesson, we learned how to _format_ the git log output; in this lesson we will learn how to _filter_ down to a specific set of commits. By default, `git log` shows every commit in a repo. We will walk through using a bunch of options to filter our git log commits to a more meaningful set (`-n`, `--after`, `--before`, `--author`, `--grep`, `-S`, `-G`, `--no-merges`, `{ref}..{ref}`, `{files}`). We will also show how all of the formatting and filtering options can be composed together to query exactly what you are looking for in your commit history.

Practical Git: Filter commit history with git log arguments

When you find a bug in an open source project, you know exactly the change you want to make. Other times you just want to find a way to contribute. Either way, you’ll need to know how the project maintainers want to run the project and work with them to come up with an implementation for the fix/feature. And if you don't even know what project to start contributing to, check out [this blogpost](https://medium.com/@kentcdodds/what-open-source-project-should-i-contribute-to-7d50ecfe1cb4) for inspiration on how to identify a good project to contribute to.

Identifying How to Contribute to an Open Source Project on GitHub

You cannot push code to repositories that you don’t own or have sufficient permission to. So instead, you make your own copy of the repository by “forking” it. You are then free to make any changes you wish to your repository.

How to Fork and Clone a GitHub Repository

Before you start making your changes, you often need to set up your environment for the changes. This is where the repositories' contributing instructions come in really handy. In this lesson we’ll get our environment set up and ready for changes.

Setting up the project locally

Often when making a change, you want to verify your approach with the maintainer or ask them for help. In this lesson we’ll make a change and commit that WIP change. Then we’ll create a pull request requesting help from the project maintainer.

How to create a Pull Request on GitHub

It’s not often that you’ll get a Pull Request on GitHub just right the first time you try. You generally will iterate with the project maintainer on your solution before your PR gets merged. In this lesson, we’ll explore some of the tools that projects use to manage contributions to open source projects on GitHub.

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