bts blockers support

AJ mentioned that he'd finished integrating my patches for bug blocking support into the Debian BTS. I hope this will prove useful in tracking both annoying blocking issues as well as transitions.

An example of the latter is the aalib transition. Every package that depends on aalib1 needs to be rebuilt to use libaa1. As part of this I filed bugs on everything that needed to be changed. I also filed a tracking bug on aalib itself, and I told the bts what bugs were blocking it.

Now I can easily just check the tracking bug every few days and watch the number of "blocked by" lines decrease to $SMALL_NUMBER, at which point I will declare the transition complete, remove the dummy transitional package, and upgrade the remaining no-longer-really-blockers to grave.

We could easily use this for all the other transitions that are currently going on, if someone has a list of bugs. For example, file a bug on general that we still have crud in /usr/doc and collect all the /usr/share/doc transition bugs as blockers. Which will also make it easy to find the packages nobody has filed a bug on yet for that transition.

I also plan to use it for coordinating some changes in the debian installer, where we often need to change a long list of things to deal with some general architectural bug (lack of unified serial console detection, udebs with broken dependencies, etc). More generally, many of the bugs filed against general are waiting for changes to different parts of Debian, which won't happen until someone files the individual bugs (with patches) to make it happen, and blockers can be used to track that work. We could also set up some yet more general bugs like "even if all RC bugs were are fixed, etch is not ready to release", and add various transition tracking bugs, todo items, etc as blockers to that etch release bug.

Of course the less grandiose use of blockers is just to let people know that their bugs are annoying you and wasting your time each time you have to read over bugs in your own bug list that you cannot fix.

Anyway, I think that's the spectrum of what that patch is capable of facilitating, which is why I wrote it, so I hope at least some of this comes to pass.