The repo is https://github.com/wtfutil/wtf/. I'd guess at it supporting macOS (brew installation) and Linux (commit messages).
$ uname -a
Linux hostname 5.2.9-arch1-1-ARCH #1 SMP PREEMPT Fri Aug 16 16:24:43 UTC 2019 x86_64 GNU/Linux
$ git clone https://github.com/wtfutil/wtf
[...]
$ cd wtf
$ make
[...]
$ ./bin/wtfutil