petervanderdoes/gitflow — pull request #19 by baby-gnu (2012-07-19 17:08:31+00:00)
Title: To finish a release, the tag must not exists or have release HEAD as its...

... second parent

This can arrive when multiple "local" release branches will be supported or actually
with the multiple "remote team" release branches.

* git-flow-release (cmd_finish): Die if an existing tags exists and its
second parent is not the release HEAD.