Command-line interfaces (CLI) are a common way to use applications. In iOS, we usually use scripting languages like Bash or Ruby to build those CLIs and automate mundane tasks. The most popular CLI for app signing and build automation is, without a doubt, Fastlane, which was initially written in Ruby. Fastlane is a great tool, convenient and fairly easy to use, and a lot of effort came into building it.
However, there's a great chance you considered moving away from Fastlane to avoid learning Ruby and to lower the entry threshold for your developers. Setting up a Ruby environment could be quite tedious and require additional devs' expertise to write and support those scripts.
Explore how to build your own command line tools with Swift in this article.