We want to export some of our CLI code to re-use in other projects. But
in Golang you cannot import code from a `main` package.
So we need to move the actual code into its own package and only have
the `func main()` in the `main` package.
As is, we'll never get any add/remove features because the flag is
set as an int 64 slice but accessed as an int slice (which has no
value, and the cli doesn't fail if the flag doesn't exist).