Both [DEB](https://www.debian.org/doc/debian-policy/ch-controlfields.html#s-f-Version) and [RPM](https://docs.fedoraproject.org/ro/Fedora_Draft_Documentation/0.1/html/RPM_Guide/ch09s03.html) support specifying an "epoch" as part of the version of a package. CMake currently does not support this which makes it difficult to create packages that can update a system package with an epoch other than 0. I currently work around this issue by using [fpm](https://github.com/jordansissel/fpm) but it would be nice if CMake would support specifying an epoch directly.