This is over engineering if I've ever seen it. For one this is a single line bash script that would allow you to even handle drag and drop. Best user experience.
It's no use to engineer something that has been solved (unless you're learning) if there are already better solutions. Even if it is an example a better one should be used.
The moral of the story should he use the best tool for the job, don't shoe horn a bad language for a into a solution, and also Google is usually the best tool for every job.
I don't think the author is really expecting people to go out and start uninstalling Python to do all their scripting in Rust. Seems to me like he saw this as an opportunity to show off the clap and glob crates, as well as write a little documentation for how to cross-compile Rust from Mac to Windows.
I'm pretty sure the author was just practicing Rust. And although in this case using Bash would be fine, in most cases you shouldn't distribute Bash scripts. They're virtually always filled with bugs and they don't work on Windows.
Overcomplicating is more like it, for engineering implies a formal specification document which includes requirements, as well as documentation to go along with the product, not to mention complete integration with the target operating system substrate.
This quickly hacked-together Rust program is light years away from that.
Second, if you're going to over engineering just look for someone who has already done that for you: http://www.den4b.com/products/renamer
It's no use to engineer something that has been solved (unless you're learning) if there are already better solutions. Even if it is an example a better one should be used.
The moral of the story should he use the best tool for the job, don't shoe horn a bad language for a into a solution, and also Google is usually the best tool for every job.