auto-update should refuse to run if -development is enabled

[broder]

The rules for -development and the rules for auto-update conflict with each other.

auto-update assumes a world with apt repository semantics, where version numbers are monotonically increasing.

-development assumes a world where things can be arbitrarily broken, and where we don't have to fix them later, where there's no guarantee we won't scribble over your harddrive, and where version numbers are convenient labels that we can change and re-write as we please.

This does bad things when, say, I upload a package to -development specifically because I expect it to break things, and then auto-update goes and installs it on a bunch of workstations.

auto-update should refuse to run if -development is enabled, because there are simply no guarantees that the end result will be a sane one.

[geofft]

I think this is a bad idea unless you have an easy way to disable this behavior. I regularly test that auto-update will DTRT with a package I'm about to upload by manually enabling -development on a cluster machine and scheduling an auto-upgrade; if we make this change, it'll prevent us from testing auto-update properly, which will only lead to pain.

[jdreed]

I think this is not what we want. I think we want to start treating -development as "alpha" and not "bleeding".

If we want a "break the world" repo, we can create one that people can deal with manually.