This is awesome, because most CLI tools for this don't seem to work anymore (at least in my experience). I need to talk to my employer, but I'd like to open source some work I've done for generating static redirects/rewrites in IIS format (still able to be used by open source .NET), as well as a tool that will take those redirects and visit the original URL, then check that a 301 redirect occurred, with the Location header set to the appropriate new URL. I work with a digital marketing agency, and we do a lot of SEO work, including making sure old URLs match up with new URLs. I got pulled into the creation of 301 redirects, so built tooling to take care of it for me.