kBuild uses a three component version number: major.minor.patch-level

For each minor release, a new branch is created. Within a minor release no changes will be made that can break compatibility. The release branch is created from the trunks x.y.0 version, and will immediately be updated to x.y.1. Version x.y.0 means that the code isn't released yet - the trunk will always be at version x.y.0.

It is desirable to have a special 'branch' which when checked out or updated will always return the current release branch.