In an imaginary world that is not very much like our current world of software development, there are no version numbers at all - only commit references. You g

In an imaginary world that is not very much like our current world of software development, there are no version numbers at all - only commit references. You generally want to upgrade to the latest high-quality commit reference available, by following an upgrade path from the commit your application is currently deployed from. Breaking changes can be identified automatically using static analysis of the commits thanks to language-level support and/or well-defined interface definitions. For all of the important workflows you use, you have external integration tests, so you can navigate the commit-space (and potentially even merge multiple paths) fairly arbitrarily with some degree of both statistical (test coverage, performance) and qualitative (feature support, hardware compatibility) confidence.