Versioning and Collaboration

This class introduces the basics of managing our code, especially in the presence of

• multiple versions of our codebase, that always exists in any non trivial software, and
• the need of collaborating with others

Specifically, we review the tools and services git and github, that were created to facilitate the "multi-person construction of multi-version software", to use Parnas' terminology.

Learning objectives

At the end of the class you should be able to:

• understand and elaborate on the benefits of a versioning and collaboration system
• understand how to use git and github
• understand how to use them "properly" (when it makes sense to commit, when it makes sense to branch, to fork, etc)
• become confident in versioning and experimenting with code and with interacting with others on the same codeabse
• understand some "best practices" for structuring a git project in terms of branching and merging strategies

Specifically, you will learn the following commands - and underlying concepts/motivations:

• init - how to start an empty repo
• clone
• status
• log
• checkout
• diff
• add - and why we have a staging area, how to use it
• commit - and commit strategies, when it is proper to commit
• merge - and solving merge conflicts
• branch - and when to branch/merge
• pull, push
• remote - setting up a remote repository
• rebase - and why/when to use it
• reset (and reset hard): when and how to revert to a state
• stash
• how/why to fork and perform pull requests

Very important: you must be able to use these commands from the command line. Otherwise you don't really understand what's happening

Reading material - required for exam

• The main material is this document (UNITN login required to access), taken in part from the Atlassian course (https://www.atlassian.com/git/tutorials/what-is-version-control#benefits-of-version-control) and then cut and extended as appropriate for this class. Note: the document is open for comments to anybody in UNITN, so you are welcome to leave your questions as comments, and we will reply in the doc, in this way everybody can see your questions and we can extend the document right away to clarify parts which were not very clear
• For the part on pull requests, instead of the above you can read about it on the github help page, which is better as we are working with github: https://help.github.com/articles/about-pull-requests/

Additional readings and material

• Pdf git cheatsheet from Atlassian. Online interactive git cheatsheet.
• A discussion on stackoverflow about navigating the commit starting from the HEAD pointer https://stackoverflow.com/questions/2221658/whats-the-difference-between-head-and-head-in-git
• Udacity course on git and github.
  • In this class you also find interesting instructions for how to configure git: https://classroom.udacity.com/courses/ud775/lessons/2980038599/concepts/33417185870923
• Master-only strategy: https://news.realm.io/news/360andev-savvas-dalkitsis-using-git-like-a-pro/
• Gitflow: https://datasift.github.io/gitflow/IntroducingGitFlow.html
• The git documentation is available at https://git-scm.com/
• some good practices https://www.git-tower.com/learn/git/ebook/en/command-line/appendix/best-practices

Practicing with git and github

• Here is a very nice webapp to learn git branches in an interactive way https://learngitbranching.js.org/
• The best way to practice is, as usual, to practice. Fork a repository on github, modify it, stage and unstage changes, create branches, etc.
• Review your familiarity of the concepts and practice with some sample exam questions on proprofs.