Git

Git is a version control system. This allows you to access multiple versions of the same directory on one disk. Git is immensely powerful, but this page will only cover the basics. If you're looking for a more in-depth reference, Julia Evans wrote a very good introduction, which you can also find in Erica's office.

Getting Started With Git

If you want to use version control on your own machine (e.g. a coding project or homework), you can create a repository, or a collection of files that git is able to keep track of and version. There are two relevant ways to create a repository: Either you're workin with something that somebody's already made, or you're starting an empty repository. In this first case, you'll use git clone, and in the second, you'll use git init.

As an example of the first, you can get the sources for this book with this:

$ git clone https://github.com/reed-cstar/guides

Cloning into 'guides'...
remote: Enumerating objects: 211, done.
remote: Counting objects: 100% (118/118), done.
remote: Compressing objects: 100% (88/88), done.
remote: Total 211 (delta 54), reused 77 (delta 30), pack-reused 93 (from 1)
Receiving objects: 100% (211/211), 632.06 KiB | 11.92 MiB/s, done.
Resolving deltas: 100% (82/82), done.

If you made changes to a repository, and you would like to track and version them, you can make a commit. A commit is the unit by which Git records changes made to some files. Alongside the content of those changes (including creations, deletions, and modifications), it also records the author, the date, and also some optional further metadata regarding the changes.

Before you start committing code, you'll need to tell git who you are. Git provides a clear interface for this with the config subcommand. Try the following, replacing the quoted vale Your Name with your name, and your.email@example.com with your email:

$ git config --global user.name 'Your Name'
$ git config --global user.email 'your.email@example.com'

Note the use of the --global flag: This instructs git to store a default value for these settings across all repositores. If you leave it out, git will associate your name and email only with the repository in your current working directory, and future invocations of git will use this value to override any global value that may or may not be set.

Now that git is sufficiently configured and you're in a repository, you can make some changes to the files and add them to the staging area with the add subcommand:

$ git add ./path/to/modified/files

With your changes added, the commit subcommand will allow you to add them to version control:

$ git commit

fatal: not a git repository (or any of the parent directories): .git

You'll see that git brings up a text editor wherein you can write a commit message. Most likely, this'll be a text editor called nano — git will run whatever command you specify in the $VISUAL environment variable. Regardless, writing some text, saving it, and exiting (via Ctrl+x in Nano) will be enough to create a commit, and you'll be dropped back in your shell.