Tuesday, December 30

Notes About Git + SVN + Google Code

I wanted to do some hacking over vacation, so I decided to pitch in and implement a feature request for Guice. Here are some of the things I learned about using Git with Google Code’s Subversion repositories:

Recommended Google Code Git Initialization
(run this in an empty directory that you would like to be a repository)

git svn clone -s --prefix=svn/ --rewrite-root=https://guice.googlecode.com/svn http://guice.googlecode.com/svn .

Note: This will pull the entire SVN repository back to its beginning. The -r argument can be used to limit the pull.

The --rewrite-root line is there so that you can remove it if you get membership status on the project and want to commit.

Additional Notes
  • Develop with Git on a Google Code Project” is a pretty good intro article that covers the very basics of using Git and connecting with Google Code.
  • An introduction to git-svn for Subversion/SVK users and deserters” seems to be the most comprehensive description of setup and use cases of Git’s SVN support.
  • Git SVN Workflow” is also a nice and friendly read.
  • Fink’s git-svn 1.6 package seems to be broken, at least for Mac OS X 10.5. It bus errors on launch. I found a fink-users thread that comments on this but provides no solution. I grabbed it from MacPorts instead, and that worked with no problem.
  • Passing the --prefix=svn/ argument to git svn init makes it easier to differentiate between server-side branches and local branches.
  • In theory, you cannot change the SVN repository URL later. In practice, it may be possible. This is particularly important for Google Code because if you check out the repository with HTTP, you cannot then commit because committing requires HTTPS for the authentication. Compounding this problem, you cannot (as far as I can tell) check out with HTTPS unless you are a member of the project. In this light, it may make sense to check out new projects using --rewriteRoot (as mentioned on the GitSvnSwitch page) pointing at HTTPS. I ended up just re-creating a new repository and using git am to move a commit between repos, as described here.
  • Use the --username argument to git svn fetch when checking out with HTTPS. You’ll be asked to type in a password (which is the random characters from your Google Code profile). Git will then save this information somewhere (I’m not sure where), so it means that you won’t have to memorize the Google Code password, or even re-specify the --username if your Gmail username differs from your username on your computer. 
  • Remember that git svn dcommit will commit to the repo once per Git commit. This will likely annoy other people on the project, so it’s best to either use git rebase -i and squash everything, or do a git reset svn/trunk and then make a single commit of the index (don’t forget to re-add new files).