Git is a modern version control system. Amongst other benefits, it allows you to save snapshots of your project allowing you view (and revert to, if necessary) previous versions of your work. This is especially critical when working in a team as you'll often need to unwind conflicting changes or figure out precisely when/what changes were made. Version control is an absolutely essential part of any software project and a little bit of time spent learning the basics will pay off many times over.
From the command line, just type:
$ sudo apt-get install git
For this class, we'll be using Bitbucket for handling remote storage of repositories (another popular service is GitHub). Although you don't need to have a remote repository (Git will work just fine locally), having a remote repository both gives you a remote backup (nice if something happens to your entire machine) and makes sharing easy if you ever need it (as you will for all assignments for this class).
Getting started is easy. First, create a new repository on Bitbucket.
Then, from the command line type:
$ mkdir /path/to/your/new/project
$ cd /path/to/your/new/project
$ git init
$ git remote add origin https://YOUR_USERNAME@bitbucket.org/YOUR_USERNAME/REPOSITORY_NAME.git
In the above examples replace YOUR_USERNAME with your Bitbucket username and REPOSITORY_NAME with the name of the repository you just created on Bitbucket (Bitbucket will also prompt you with these commands after creating a new repo).
After creating a repository and linking it to Bitbucket, you'll want
to get to work. Let's say you've started a new file called "test.py"
and, after getting a few lines in, want to save your work. From the
command line in your project directory, just type:
$ git add test.py
$ git commit -m "adding test.py (or whatever message describes your work)"
$ git push origin master
Let's look at each of those commands.
git add test.py
tells git that this is a file you
want under version control (often there will be plenty of files, for
example temp files or compiled files that you wouldn't want in version
control).
git commit -m "some message"
is what actually
commits (stores) your changes locally. Every commit is required to have a
commit message. The -m flag allows you to directly enter that message
on the command line (in quotes). Although it may seem like a waste,
descriptive commit messages can be extremely useful when trying to
remember what you did (and even more so when working in a team and
trying to figure out what someone else did!).
git push origin master
is what actually pushes the
changes up to your remote repository. It's very easy to forget this
final step (especially if you're used to some other version control
systems), so make sure to get in the habit of always pushing your
changes after a commit.
If you are working in a team or just working on multiple computers and want to pull down the latest version of your work, there are two commands you need to know.
If you are pulling down an existing repository for the first time, use the clone command. For example:
$ git clone https://YOUR_USER@bitbucket.org/YOUR_USER/REPO_NAME.git
If you already have a copy of the repository and just want to pull down the latest changes, just use the pull command. For example (from your project directory):
$ git pull
During a pull, if there are parts of the code that need to be merged (for example, if two people have modified the same file), git will prompt you to resolve any conflicts. This is far superior to just overwriting each other's work!