Although it has a slightly different focus, I advise reading up on Bundler, the Ruby library versioning tool created by Yehuda Katz to bring sanity to rails plugins.

It has an interesting version symbol to indicate upgrading along a major version:

~> 1.1.0

That will allow 1.2.0, but not 2.0.0.

Bundler also has the idea of version locking across the transitive closure.

--
Sent from my CyanogenMod-powered
Android device, an open platform for
carriers, developers and consumers.