It would be nice if reprepro had the possibility to clone
a distribution under a new codename/suite.

Since this requires editing conf/distributions I would understand
if you opted to only document a sane way to do this... and not do
everything automatically (although to be fair, it would also be nice
if conf/distributions could be replaced with a set of
debian/distributions/<codename> files).

I know of the snapshot command but here I really want a new distribution
that can evolve and that has a name unrelated to the distribution being
cloned.

For now, I'll do this and assume it's ok:
- cp -a dists/srcdist dists/targetdist (this ensures that I copies over
  also the installer files)
- create "targetdist" in conf/distributions with a pull rule pulling
  everything from "srcdist"
- do a "reprepro pull targetdist"