While it is simpler to compare a monotonically increasing integer (the revision), we always use the semantic version string in the user interface, meaning that this version string should change together with the revision, which effectively means we are maintaing two version numbers.
We previously embedded the revision in the version string (2.0-alpha.$revision) but when going from alpha → beta, it would be nice to reset the visible counter, so that first beta becomes 2.0-beta.1, furthermore, test versions could benefit from a more descriptive version string, e.g. “2.0-alpha.9439.2+debug” would be the second (semi-public) debug build after “2.0-alpha.9439”.