Took 2 days in a row off, because I noticed I have forgotten to do that
since February, or possibly earlier, not counting trips. Whoops!

Also, I was feeling overwhelmed with the complexity of fixing XMPP to not
be buggy when there are multiple separate repos using the same XMPP
account. Let my subconscious work on that, and last night it served up the
solution, in detail. Built it today.

It's only a partial solution, really. If you want to use the same XMPP
account for multiple separate repositories, you cannot use the "Share with
your other devices" option to pair your devices. That's because XMPP
pairing assumes all your devices are using the same XMPP account, in order
to avoid needing to confirm on every device each time you add a new device.
The UI is clear about that, and it avoids complexity, so I'm ok with that.

But, if you want to instead use "Share with a friend", you now can use the
same XMPP account for as many separate repositories as you like. The
assistant now ignores pushes from repositories it doesn't know about.
Before, it would merge them all together without warning.

----

While I was testing that, I think I found out the real reason why XMPP
pushes have seemed a little unreliable. It turns out to not be an XMPP
issue at all! Instead, the merger was simply not always
noticing when `git receive-pack` updated a ref, and not merging it into
master. That was easily fixed.

----

Adam Spiers has been getting a `.gitignore` query interface suitable for
the assistant to use into `git`, and he tells me it's landed in `next`.
I should soon check that out and get the assistant using it. But first,
Android app!
