StepUp is a tool to manage versioning. That means you can bump the version of your project, for example, from v3.0.11 to v4.0.0, check the current version, summarize all the history of versions in a changelog and more.
StepUp is based on source control management features (i.e. tags, branches, commits, notes etc), so it doesn't need to keep files with the current version (but it supports it, if you want), it has visibility of all history of changes and versions (doesn't matter if they are spread in many different branches), which adds a variety of possibilities in terms of management, depending on your project needs.
The original project is a Ruby GEM named step-up, and the goal of this project is to transcribe the main features of the original utility into a git-command by using other native scriptable languages (like Shell and/or PERL).