The maintainer's half of gem_kit: one RubyGems command, `gem kit`, with subcommands for bumping the version, writing and linting the changelog, listing outstanding deprecations, releasing and tagging. It keeps the promises gem_kit records. `gem kit bump` refuses to move onto a deprecation's removal version while the old name is still in the tree, and `gem kit release` refuses to ship a version with an unkept promise or no changelog entry of its own. Everything is read from the .gemspec in the working directory, so the normal case needs no configuration at all.