Over the last couple of years I have released a bunch of libraries under Open Source licenses, usually on Google code. However the my last project, OpenPyro was a little different and was released on GitHub with Git as the Version Control System. I write this as a developer with more experience and comfort using Subversion and yet encourage you to release your open source projects on Git.
So what is Git? The one line description (from Wikipedia) is “Git is a distributed version control system, born with the fundamental mechanisms making branching and merging really easy.” A detailed description of Git is beyond this post but the Wikipedia page is a good place to start.
Releasing OpenPyro on Git was not an easy decision to make. The project represents a lot of work on my part and I am nowhere near as comfortable yet with Git as I was with SVN. I definitely did not want an unfamiliar Version Control System deter possible contributors to the project. However the fundamental philosophy of Git was what finally won me over.
The Git workflow is kind of new (at least to me). A developer working on a project begins by forking the core repository. He can commit code to his fork at his whim and needs to keep merging from the original branch to get the latest updates from there. Its up to him to merge changes from the core repository as they happen. People working on different forks merge changes from each other as they see fit (if you are working in a non-distributed environment, you can all merge off of a source of truth repo)
Forking basically allows the project to achieve velocities greater than the initiator of the project. If tomorrow I stop working on OpenPyro, there could be a fork that has developers more committed than I could be. Why should OpenPyro stall just cause the original developer may have.
As of right now OpenPyro has been forked a couple of times. The first fork was for a Haxe port and this was before OpenPyro was on GitHub so it wont show up on the network graph on Github. The second fork was by Kelvin Luck who fixed a few bugs on his branch and is adding new functionality there. However he didnt have to wait for me to commit his changes into OpenPyro head. I merged his changes into the OpenPyro head much later. And now the OpenPyro history shows his additions to the project as official commits.
The diagram below shows the state of the repository as it got branched and merged at different times.
This kind of collaboration wasnt possible with SVN, something I realized while working on LogBook. I would get patches for bugs on the project, sometimes feature updates I didn’t much care about. But it was up to me to add those in, and sometimes time pressures made me miss commiting some features forcing the developer on the other side to wait with probably changes local to his machine.
I have been on the receiving side of that as well and I am sure you have as well. How many times have you looked at an open source project that seems to fit the bill for what you are working for but comes up slightly short. What do you do then ? Do you fork it? Without commit access to the core repository that the original author is maintaining, you cannot branch the project. All you can do is export all the files and recommit them into a new repository that you control. But now you have lost the project history (plus something about this approach just smells wrong, with very little attribution on the “forked” repository to the main project).
There are other features that are great in Git. Offline commits is another great feature that I use quite a bit. A more detailed comparison against SVN can be found here
Whether this paradigm works as well within teams working together, I am not sure. At work we continue to use SVN right now and I am not sure if we plan to move off it anytime soon, But if you are a developer releasing code under open source, I strongly encourage you to try Git. In the meanwhile here are some resources that you could find useful. Linus Torvald’s talk at Google is a good place to start understanding Git philosophically.