This repo provides RPM packaging for facebook/watchman. This repo is used to build the eklitzke/watchman Fedora COPR repository, which you can use to get pre-built RPMs.
To install watchman using my COPR repository:
# Enable the eklitzke/watchman copr repository.
$ sudo dnf copr enable eklitzke/watchman
# Install the watchman RPM.
$ sudo dnf install watchman