Software and revision control

Small intro to revision control with Git

Emphasis on concepts over details. Concretely, knowing concepts

• makes it easier to find the details
• helps to understand the error messages :)

What is revision control and what are Git and GitHub?

• source code with history, and much, much more

Let’s find out!

Why Git and Git repository servers?

• encourages to think “programming” as more organized software development
• provides safety net and a framework for collaborative software development
• integration to other services, such as GitHub Pages
• many options for remote repository hosting, GitHub*, Bitbucket**, and University’s GitLab server***

What was it like before revision control, Git and remote repositories? Tarballs and directories with files in some state scattered in mailboxes and in various machines and user accounts?

* https://github.com
** https://bitbucket.org
*** https://version.helsinki.fi

What to put into a source repository?

Source code, of course!

• basically anything that someone has typed
• Commit new features, bug fixes, etc, instead of modifications in single files

What not to put into source code repository?

• binary data: jpgs, data sets, executables, pdfs, PowerPoint slides
• automatically generated text, program output

This keeps the repository small and quick to work with.

Local Git repository

The most important concepts are described in Git Basics*, especially the last section, “The Three Stages.”

What git command

• moves (adds) files from Working Directory to Staging Area?
• moves (commits) files from Staging Area to Repository?
• moves (checkouts) files from Repository to Working Directory?

Draw a picture!

A bonus exercise: commands that move files to opposite directions?

* https://git-scm.com/book/en/v2/Getting-Started-Git-Basics

The Three Stages

Remote Git repository

Let’s just dive into it!

• create GitHub account
• fork this upstream repository
• clone your forked remote repository into a local one

https://help.github.com

Config and Branches

Some first things to try:

• tell (set/config) git your name and email address
• list all branches

Some pointers:

• https://help.github.com/categories/setup
• https://github.com/joshnh/Git-Commands
• http://rogerdudler.github.io/git-guide

There’s plenty more good docs in the internet. Collect you own set!

Wrapping up

Find the commands that do the following tasks, and *draw a picture * (you can work together!):

• how to push your changes in the local repo to your forked repo
• how to fetch changes in the upstream repo to a branch in your local repo
• how to merge upstream branch into your master branch

Drawing the picture is most important. If you actually can do this now, you are pretty skilled in using git!

Merry-go-round

Where next

• NeIC Coderefinery has an extensive Git course*, lectures** at Aalto University 11.12.2018.
• practice, experiment, explore, find your own way!

Test: What is the difference between pull and fetch?

* https://coderefinery.github.io/git-intro
** https://coderefinery.org/workshops/2018-12-11-espoo