prune prunes too much?

[ThomasWaldmann]

I didn't practically try it, but the code looks like prune is not used with --prefix option.
In this case, prune specification applies to all archives in the repository.

If one backs up multiple clients (or in general: multiple data sets) into one rep, it will likely delete archives that should not get deleted.

So, if archive names are like hostname-datasetname-timestamp, we should use --prefix hostname-datasetname- and the prune options should be set per hostname-datasetname combination.

[m3nu]

I didn't consider this use case. To avoid unexpected prunes, I added platform.node() as prefix. The create subcommand uses it as prefix as well.