#GitHub vs git
- git (lowercase) is a version control system. There are many like it, but this one is ours. It is free and available for anyone to use. git is usually used from a command prompt.
- GitHub is a company that allows you to save your code to their servers so that anyone can access it from anywhere. GitHub relies on git to manage the state of your code. GitHub has created an app that you can use to issue git commands, so you don't have to use the command line if you don't want.
This is a getting-started guide for the command line.
#Terminology
repo: Short for "repository." This is your code's home. All of your code's change history is kept here, too.
branch: A copy of the repo. One repo will have many branches. Ever made copies of a document to save prior states, like "essay-edits.doc," "essay-v2.doc", "essay-final-final.doc"? Those are basically all branches of a document called "essay.doc." git branches are similar, except they make it easy to fold your edits back into the main branch (which is usually called something like master or develop).
commit: A granular change that is ready to become part of your branch. You will select files to commit, write a message describing the change, and save the change to the branch.
#Common tasks This is far from a complete list of things you can do or need to do with git, but my goal is to make the general workflow simpler to understand for those new to git and the command line.
##Getting code from GitHub onto your computer
git clone your-repo-url
Go to the repo on GitHub (for instance, https://github.com/18F/calc). Click the "Clone or Download" button and use the SSH URL. This will create a folder named, in this instance, calc. (You only need to do this once per repository.)
##See which branches are available locally
git branch -l
(The -l is called a flag in command-line speak and it stands for "list.")
##Make new branches available locally
git fetch
Say you know someone has pushed up a new branch, and you want to work on that. This will make your local codebase aware of new branches.
##Change which branch you're on
git checkout a-branch-name
##Making a new branch
git checkout -b your-branch-name
You do this if you are making changes that might break the main repo, experimenting, or otherwise creating things that need to be approved and reviewed.
##See which files you've changed
git status
(Shows a list of files changed.)
##Choosing changes to save with git
git add your-file-name
-or-
git add directory/*
(adds everything in a directory)
-or-
git add .
(adds everything that has changed)
##Saving changes with git
git commit -m "a message describing the changes made"
##Getting changes that other people may have pushed to the branch you're on
git pull origin your-branch-name
##Making your changes available to other people working on your branch
git push origin your-branch-name