Backups storage

Add a backups archive storage abstraction and do a little cleanup.
I know what you mean.  I've taken to routinely adding that comment because it really isn't clear when you first pick up the language (idiom or not).  It's tricky because the line doesn't actually do anything at runtime (at least in the more idiomatic form I'm switching to in a sec), though at first glance it looks like it does.  So without the comment it's easy to miss that this is a compile-time check with a specific purpose.  If you don't mind, I'll leave the comment in, but refrain from similar comments in the future.