How do I either “unrm” in git repository or move files from one repository to another

Question

I have a large rails project currently using rails 2.3.11 and I want to migrate it up to rails 3. I had an idea that I'd like to try but I need some git help.

What I want to do is start from a fresh new rails 3 app. One idea is to get in my current rails project directory and delete everything. Then do a commit so the tree is empty. Then create a new rails 3 project. This way I am starting fresh so everything will be current.

Then as I add the old controllers, etc back into the project, I want to "unrm" them. Git knows the history of the files and I'd like to keep that history.

Another alternative would be to start a fresh rails 3 app and then somehow transport files from the old git repository to the new git repository but I'd like to keep the history of the file.

This is a half baked idea but it seems a more viable approach to moving this particular project is to essentially start over fresh and then move things from the old project into the new project. But when I move things from old to new, I'd like to keep the history of each particular file.

Can anyone suggest a method of doing what I've just outlined?

Answer 1

First: check out this to automatically find some of the things that need to be upgraded: https://github.com/rails/rails_upgrade

To answer your question: You can upgrade your rails gem and then run rails new . to generate a new rails 3 app on top of your rails 2 app. It will clobber a few of your important files, but you can use git diff to figure out what was in them and copy the important things into the new file. Finally, there's a few things you might need to manually delete (like all of the files in the script/ folder except for rails). "Generating" a new rails 3 app on top of your existing app seems to be the recommended practice, and worked well for me when I upgraded a rather large and old app.