Maintain your program versions entirely within git. No local files required! All
versioning information is stored using git tags.

This gem contains a command-line tool and set of Rake tasks to increment and
display your version numbers via git tags, and some associated Ruby code to use
inside a gemspec or your program to retrieve the current version number, for use
in builds and at runtime.

WWW: https://github.com/mpalmer/git-version-bump