Software changes, interface compatibility breaks, old functionality becomes deprecated in favor of improved implementations. With a consistent versioning scheme users can immediately determine whether or not an upgrade to their library will cause problems with compilation or linkage or if a new version of their end user software might cause disruptions to their existing workflow.
Consistency in versioning helps developers choose non-breaking changes when determining what changes could be backported to older maintained versions. A version increment denotes a step in the software lifecycle. As a part of managing user expectations, the version increments should match the significance of improvements and features implemented.
Semantic versioning 2.0.0 , SemVer for short, is a de facto standard for open source libraries and utilities. It provides a clear distinction between versions that are:
Minor bugfixes or changes that do not alter the interface (patch)
Backward compatible, but might deprecate some features or introduce new ones that do not require major adjustments from the end user (minor)
Backwards incompatible, require the user of a library to modify or re-implement the code interfacing the library or the user of a desktop application to adjust their way of working with the software. (major)
For continuous deployment systems, the use of semantic versioning requires some planning on deciding when to increment the major and minor versions. If the change is not considered significant, only the patch number is incremented.
A benefit of using SemVer for versioning is the automatic merge feature of BitBucket that allows you to make patch-level changes in a feature branch off the earliest required version and have the feature branch automatically merged to later major and minor versions upon merging.
Some versions, such as public releases and service packs, can be labelled separately from the used version scheme. Those versions can be referred to by internal and external versions (e.g. “Windows XP SP3” vs “Build 4608”).
Git SHA1 hashes can be considered internal versions, as long as the repository is available.