Mephisto: Change from SVN to Git April 19th

The fine folks over at ENTP/ActiveReload have released version 0.8 of Mephisto, the Rails application that powers this site. With this new release, they, as everyone these days, have actively shifted the remaining bits and pieces of Mephisto’s development from Subversion to Git. (And its main repository is hosted at Github, where else.)

I hardly remember ever installing Mephisto from a tarball. I always used to track its Subversion trunk for the 3 blogs I run, which made upgrading as easy as svn up && rake db:migrate RAILS_ENV=production most of the time. Well, that was then and this is now. Looking at this recent shift to Git, I wanted to convert my blogs to the new Git repository without excessively messing with whatever I did to my local installation (quickly approaching my 30s, I might not even recall most of what I did). I was pretty certain, however, that I did not have massive local modifications. If I had, this approach might’ve been a little simplistic.

Here’s what I did.

Initializing

Starting out, you need to create a local Git repository within your local blog installation, which is as simple as:

$ cd /your/blog
$ git init
Initialized empty Git repository in .git/

The next step is to setup technoweenie’s master repository on Github as a remote to your local repository and fetch what’s currently in there.

$ git remote add technoweenie git://github.com/technoweenie/mephisto.git
$ git fetch technoweenie
remote: Generating pack...
...

This will fetch both the master branch and all branches technoweenie might’ve created. (This includes, for example, a branch that holds the current 0.8 release, if you don’t dare to ride the edge of Mephisto’s development.)

Merging

At this point we need to merge one of the branches we just fetched into your local (totally empty, for what it’s worth) repository. (I’ve decided to stay on the master branch. If you prefer a release branch, substitute it as appropriate.)

$ git merge technoweenie/master

Since Subversion scatters its .svn folders all over the place, we need to get rid of those. You can either do that manually or with a little find-fu.

$ find . -type d -name '.svn' -exec rm -rf {} \;

Excellent, that’s much better. Now it should be safe to check out the current state of affairs:

$ git status

Running this command will show you the currently untracked files. Those would be all files that existed locally before you started to create your own Git repository and which are non-existent in technoweenie’s repository.

Tracking local modifications

As I mentioned above, I didn’t have a boatload of local modifications. My changes were limited to bit of configuration, a few third party plugins (and the accompanying CSS/Javascript) and my local Mint installation. The additional files and directories that may show up are the cached HTML files that Mephisto sticks in public/.

To actually add your local modifications to your Git repository, simple add and commit them.

$ git add config/mongrel_cluster.yml
$ git commit -m 'Mongrel configuration'

If you’d prefer to rather ignore whatever else sits in your blog directory, add it to .gitignore

$ echo "public/*.html" >> .gitignore
$ echo "public/200*" >> .gitignore
$ echo "public/mint" >> .gitignore
$ git commit -m 'Ignore cache and mint' .gitignore

Cleaning up

I had a few files sitting in my directory that weren’t local modifications but seemed to have been removed from the official repository, too. Those weren’t caught by our merging of the Git branch since we started with zero history. To get rid of those, let’s take a look at git-clean.

$ git clean -n -d
Would remove app/views/admin/article_comments/
Would remove app/views/admin/articles/approve.rjs
Would remove app/views/admin/articles/comments.rhtml
Would remove app/views/admin/articles/destroy_comment.rjs
...

The -n argument prevents git clean from actually doing anything. If you’re confident it wouldn’t do anything harmful, go ahread and remove it. (You do have backups, right? Do you?)

At this point we’re down to regular upgrading business, so you might want to run the migrations and restart your Mongrel cluster. (Or whatever floats your deployment boat.)

$ rake db:migrate RAILS_ENV=production
$ mongrel_rails cluster::restart

Into the future

Now, whenever Mr. Weenie adds an exciting new feature to Mephisto you can grab that via:

$ git fetch technoweenie
$ git merge technoweenie/master

Or if you’d rather prefer to pick a specific commit:

$ git cherry-pick <SHA1>

Further reading

Since this is not a Git guide per-se, I’ll end the article at this point. There is plenty of other content available online to bring you up to speed with Git.