What’s git, and why do you use it?
Monday, June 30th, 2008At Freelock, we’re always trying to figure out ways to do things better. Recently I started digging into a developer tool that’s making, as Bryan over at the Linux Action Show would say, my head explode.
For a long time, we’ve managed our custom code projects and business documents in a central repository, called Subversion (also known as svn). Subversion is relatively easy to understand–it’s like having a library of files you can check a copy out of, do some work on it, and then check it back in. Subversion is the librarian that tracks who has copies of what, and when they checked it out. So if Erik checks in changes to a brochure, and then Jill goes to submit changes to the same document, Subversion will say “hey wait a minute, that document has already been changed–you need to make sure you put Erik’s changes in your document before I’ll let you put in your document.”
This is great for managing conflicts between people working on a single team, or for code that is being developed in relative isolation from the rest of the world.
The problem is, we’re doing more than that–we’re taking code from various open source projects and either customizing it or building new applications on top of it. And so when the outside projects get updated, we need to manually update anything we’ve written that depends on that code. There is no longer a single repository where we control our code–there is our code library, plus another one for every project we use.
This makes managing add-ons for projects like Joomla or ZenCart quite challenging, because our add-ons get scattered throughout the filesystem to be able to hook into the right place. And if we have to touch a core file, we’re going to end up needing to re-implement our change with any update to that core file.
There are other issues we run into, managing our code and hosting, all of which take fairly time-consuming, manual intervention. Here’s the list:
- Since we host and provide security updates for Joomla, Word Press, Zen Cart, Drupal, and others, we need to upgrade dozens of installations any time there’s a new release that has a fix for a security vulnerability. With Joomla this has happened quite a lot, and every Joomla installation needs to be upgraded individually–and tested. And since each installation is slightly different, we can’t manage them easily within a single repository, while updating the underlying code.
- Templates, modules, components, blocks, themes, plugins, and whatever. Developing these types of add-ons are our bread-and-butter. But code for these often get scattered across an installation, making it quite difficult to manage just our add-ons while we develop them, or roll back to earlier versions if there’s a problem.
- The Dojo Toolkit, and builds. We’re doing a lot of development with Dojo right now, to add desktop-like functionality such as trees, sortable tables, right-click menus, animations, and lots of other really cool things. However, if you don’t “build” the code after you write it, it’s painfully slow in a web browser. And due to the nature of how Subversion works, you can’t easily store a built Dojo tree if you ever want to change it again. Which means you’d need to build it every place you deploy it. And on some computers, it can take a long time to build–on our demo server, one of our projects currently takes 8 minutes.
- As we get more directly involved with open source projects like LedgerSMB, we’re finding the need to change core files while we hack away at some particular feature. To do this, you create a branch of the code, work on your feature, and then merge your changes back into the “trunk.” If you don’t have access to save directly to the project repository, doing this gets a lot more complicated.
Git to the rescue. Git solves all of these issues. Read on for a technical discussion of how.
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