Paul Dowman

When I was moving EC2 on Rails to Git I found several posts that explained how to convert a repo from svn to Git. But none of them included converting your svn tags to Git tags, so here’s yet another how-to guide. (Git experts please comment if I’m doing anything dumb.)

1. Install Git

First, you’ll need Git installed with git-svn included (git-svn will actually allow you to push changes back to the original Subversion repository, but for our purposes we’re assuming that this is a one-time conversion).

If you’re using OS X you should already be using MacPorts, so just do:

prompt> sudo port install git-core +svn

Or, on Ubuntu or Debian Linux:

prompt> sudo apt-get install git-svn

2. Create the authors file

Next, create a text file that maps Subversion committers to Git authors so the names and email addresses will be correct in the history. Save it as authors.txt:

pdowman = Paul Dowman <paul@hellospambot.com>
svnuser2 = Another User <anotheruser@whatever.com>

3. Clone the repository

Now run the command that will import your svn repo into a local Git repo. I’m assuming your svn repo had the standard layout of /trunk, /tags and /branches.

prompt> git svn clone --no-metadata -A authors.txt -t tags -b branches -T trunk <your_svn_url>

Now running git log should show all your commit history with the correct authors.

4. Convert branches to tags

There’s one more thing. All your tags are now remote branches, not tags, in your Git repo. So you’ll need to convert them manually (or write a script to do it if you have a lot, I’ll leave that as an exercise for the reader). For each Subversion tag (i.e. Git remote branch) you’ll add it as a Git tag, then delete the remote branch. List them with:

prompt> git branch -r

Then for each tag listed do:

prompt> git tag tagname tags/tagname^
prompt> git branch -r -d tags/tagname

You now have a local Git repository with all your history and tags. If you don’t need to share it with anyone else then you’re done.

5. Push to a public repo (optional)

If you want to publish to a public repository (for example Github), you’ll need to add it as a remote repo and then push to it.

prompt> git remote add origin git@github.com:userid/project.git
prompt> git push origin master

You next stop should probably be the Git tutorial for Subversion users. Enjoy!

I’ve moved EC2 on Rails from Subversion to Git. It’s hosted on Github at pauldowman/ec2onrails.

Most Ruby developers are familiar with Git by now. (If you’re not: it’s a distributed version control system that was created in 2005 by Linus Torvalds for Linux kernel development). Within the last year almost every Ruby-based open-source project has switched to Git (including Rails itself). And in fact they’re almost all hosted on Github!

At first I found it funny that even though they were moving to a distributed version control system, everyone decided to keep their repositories in the exact same place. Being distributed, a Git repository doesn’t need to be hosted unless you’re sharing it. You can publish it easily on any web server, and RubyForge (which has always been the most popular place to host Ruby projects) supports git.

But after playing with it a bit I can see why everyone is choosing Github. For one thing they got the project hosting part right, with a simple clean UI and cool features like an API and hooks for all kinds of services.

But the really cool thing about Github is that it provides a social environment. You can watch projects as you’d expect, but you can also follow people, send them messages, and easily send them pull requests (to integrate changes you’ve made). It’s great for discovering interesting and new projects: just follow friends and people whose work you like to see what they’re watching, creating and forking.

Now that EC2 on Rails is on Github it’s more likely that other people will want to build it themselves so I’ll try to make that easier with a one-step script at the root of the project. Feel free to fork it, implement changes and send me patches or pull requests.

And find me on Github!