previous episode

Version control with Git

next episode

Working from multiple locations with a remote repository

Overview

Teaching: 25 min
Exercises: 0 min
Questions

  • What is a remote repository

  • How can I use GitHub to work from multiple locations?

Objectives

  • Understand how to set up remote repository

  • Understand how to push local changes to a remote repository

  • Understand how to clone a remote repository

We’re going to set up a remote repository that we can use from multiple locations. The remote repository can also be shared with colleagues, if we want to.

GitHub

GitHub is a company which provides remote repositories for Git and a range of functionalities supporting their use. GitHub allows users to set up their private and public source code Git repositories. It provides tools for browsing, collaborating on and documenting code. GitHub, like other services such as Launchpad, Bitbucket, GoogleCode, and SourceForge supports a wealth of resources to support projects including:

Note GitHub’s free repositories have public licences by default. If you don’t want to share (in the most liberal sense) your stuff with the world and you want to use GitHub, you will need to pay for private GitHub repositories (GitHub offers up to 5 free private repositories if you are an academic — but do check this information as T&C may change).

GitHub for research

GitHub isn’t the only remote repostitories provider. It is however very popular, in particular within the Open Source communities. The reason why we teach GitHub in this tutorial is mainly due to popular demand.

Also, GitHub has started working on functionality which is particularily useful for researchers such as making code citable.

Get an account

Let’s get back to our tutorial. We will first need a GitHub account.

Sign up or if you already have an account sign in.

Create a new repository

Now, we can create a repository on GitHub,

You’ll get a page with new information about your repository. We already have our local repository and we will be pushing it to GitHub, so this is the option we will use:

$ git remote add origin https://github.com/<USERNAME>/conversions.git 
$ git push -u origin master

The first line sets up an alias origin, to correspond to the URL of our new repository on GitHub.

Copy and paste the first line now.

Push locally tracked files to a remote repository

Now copy and paste the second line,

$ git push -u origin master 

Counting objects: 32, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (28/28), done.
Writing objects: 100% (32/32), 3.29 KiB | 0 bytes/s, done.
Total 32 (delta 7), reused 0 (delta 0)
To https://github.com/gcapes/conversions.git
 * [new branch]      master -> master
Branch master set up to track remote branch master from origin.

This pushes our master branch to the remote repository, named via the alias origin and creates a new master branch in the remote repository.

Now, on GitHub, we should see our code and if we click the Commits tab we should see our complete history of commits.

Our local repository is now available on GitHub. So, anywhere we can access GitHub, we can access our repository.

Push other local branches to a remote repository

Let’s push each of our local branches into our remote repository using the same syntax as before:

$ git push origin branch_name

The branch should now be created in our GitHub repository.

To list all branches (local and remote):

$ git branch -a

Deleting branches (for information only)

Don’t do this now. This is just for information. To delete branches, use the following syntax:

$ git branch -d branch_name			# For local branches
$ git push origin --delete branch_name		# For remote branches

Cloning a remote repository

Now, let’s do something drastic! (but before that step, make sure that you pushed all your local branches into the remote repository)

$ cd .. 
$ rm -rf conversions

Gulp! We’ve just wiped our local repository! But, as we’ve a copy on GitHub we can just copy, or git clone that,

$ git clone https://github.com/USERNAME/conversions.git 

Cloning into 'conversions'...
remote: Counting objects: 32, done.
remote: Compressing objects: 100% (21/21), done.
remote: Total 32 (delta 7), reused 32 (delta 7), pack-reused 0
Unpacking objects: 100% (32/32), done.
Checking connectivity... done.

Cloning creates an exact copy of the repository. By default it creates a directory with the same name as the name of the repository.

Now, if we change into conversions we can see that we have our repository,

$ cd conversions 
$ git log

and we can see our Git configuration files too:

$ ls -A

In order to see the other branches locally, we can check them out as before:

$ git branch -r					# Show remote branches
$ git checkout newton				# Check out the newton branch

Push changes to a remote repository

We can use our cloned repository just as if it was a local repository so let’s make some changes to our files and commit these. We’ll work on the master branch to create a plot of Fahrenheit vs Celsius.

$ git checkout master				# We'll continue working on the master branch

Edit temperature_conversions.m to contain the following code at the end:

% Plot Fahrenheit vs Celsius
degC = linspace(0,100,101);
plot(degC, celsius_to_fahrenheit(degC))
xlabel('Celsius')
ylabel('Fahrenheit')

Now stage and commit the script

$ git add temperature_conversions.m
$ git commit						# Write a suitable commit message

Having done that, how do we send our changes back to the remote repository? We can do this by pushing our changes,

$ git push origin master

If we now check our GitHub page we should be able to see our new changes under the Commit tab.

To see all remote repositories (we can have multiple!):

$ git remote -v

Key Points

  • Git is the version control system: GitHub is a remote repositories provider.

  • git clone to make a local copy of a remote repository

  • git push to send local changes to remote repository

previous episode

next episode