How to automatically merge modifications in multiple projects?

I'm working on a Ruby on Rails (3 beta) project whic开发者_如何学运维h is basically a simple back-office with users, contents and localizations. This back-office will be our start for all news projects. However this base isn't perfect and might be widely improved.

I would like to keep improving this base during the development of the new project. But to do so I might need to duplicate the modifications. Do you know a way to do this automatically ? By this I mean automatically merge modifications done to the base into all projects using it and vice versa.

We are using SVN and thinking about using Git or SVN with "Piston". Are we looking in the good direction ?

If you are maintaining common code that is used by multiple projects, you should read up on externals definitions and vendor branches to see if either of those will work for you.

Yes you're moving in a good direction. Problems of the sort you describe are among the reasons people use version control. And yes, version control systems allow multiple changes to be merged together.

But if by "automatic" you mean "propagated by the version control system to all my other projects" - it won't happen. You'll have to checkout the new code and rebuild each project.