Revision control systems like Git are important for today's software ecosystems to help build better scientific software and improve developer productivity on a project.
Introduction
Revision control systems like Git are important for today's software ecosystems to help build better scientific software and improve developer productivity on a project.
In this article, we provide a valuable collection of tutorials and reference information about the Git version control system. This overview takes the view that the best way to learn to use Git effectively is to learn it as a data structure and a set of algorithms to manipulate that data structurewthigsh.
Git is currently the dominant version control system and is used worldwide. Nevertheless, the Git command-line interface is considered by many to be overly complex and confusinggvmwg. For example, the same Git command like checkout can do wildly different things depending on the other arguments that are passed into the command, or the state of the Git repository. The following resources have shown recurring utility in helping to understand and effectively use this sophisticated but quirky tool.
Links to Git tutorial and reference material
For a full-featured introduction and reference for Git, a good source is the free online book:
- Pro Git: 2nd Edition by Scott Chacon and Ben Straub
Pro Git is a comprehensive and detailed book with a lot of valuable information. For folks who find comprehensive books intimidating but are still looking to find specific Git information - we also provide below some other shorter and more targeted references that may be helpful to understand Git and one may want to consult them day-to-day usage of Git.
(NOTE: Since the publication of Pro Git 2nd edition in 2014, many other Git books have come along and many of them are likely to cover newer Git features. But the core of Git is unchanged since before 2008 and this book is still near the top of recommended books to read about Git.)
Assuming you are a complete Git beginner and can’t wait to start contributing to a Git repository, you would be wise to first take note of:
After that, for a nice (relatively short) visual reference for common Git operations, see:
A nice interactive visual tutorial (and simple Git simulator) and reference for common Git operations is:
Another similar site is:
The Learn Git Branching site is more interactive with more guided lessons than the Visualizing Git Concepts with D3 site.
It also supports more Git commands like git cherry-pick and it allows for larger Git simulations.
One could try out the sandbox mode to do quick unguided Git workflow simulations.
However, this is still just a simulator for Git so it does not support all Git commands and options.
To really be able to use Git well, you have to know a little bit about how it works and how it stores changes to a repository. To help understand this, a nice short overview of the Git object model is given in:
The data model for Git is not very complicated as data structures go; it is that of a directed acyclic graph (DAG) where each node in the graph is a commit that represents a specific version (or snapshot) of the repository (repo). The edges in the graph between adjacent nodes/commits represent patches or differences between the different versions of the repo’s files and provide the "history" of the changes of the repository. Once you see how Git stores the different versions (snapshots) of a repo, you can use that information to understand the impact of various decisions and operations. The Visual Git Reference and nearly every other Git reference refers to this DAG of Git commits in some way. A more technical description of the Git object model is given in the Git Pro Object Model chapter. (Git also uses a more compact storage format called Packfiles that can store deltas to changes in files for older history.)
For those that have the time to work through a longer online tutorial, consider taking the following excellent course which teaches both the basics of version control and Git as well as how to look at Git from a data structure perspective:
- Version Control with Git from Udacity.com
The above online course is broken down into well-named sections so you can browse the course to find topics where you would like to see someone explain it in simple language, diagrams, and examples.
Here are some short Git cheat sheets that some may find useful:
- Git Cheatsheet (from Tower)
- Git Cheatsheet (interactive page from NDP Software)
(The latter Git Cheatsheet from NDP Software graphically shows how git commands move data between the various Git "places" and is a good complement to the Visual Git Reference.)
Here are some useful pages with various information about Git:
- First Aid Git (includes search of FAQs)
- How to undo (almost) anything in Git
In addition to the above, a web search will yield many additional resources.
