[packagekit] Message to backend authors

[Richard Hughes]

Hey people,

I've pushed a few more backend API changes to master yesterday; I
think I've fixed up all the backends, but could you please check out
master and check that everything still compiles. If you've not yet
ported to PkTransactionFlags, this also might be the time to do it.
See backends/PORTING.txt for details. Ignore the parts about parallel
transactions, that's not applicable just yet.

Next week I'm going to merge a much more disruptive patch which I've
been working on with ximion to allow parallel transactions, but I'm
still chasing critical-warnings and fixing up the self tests. Again,
I'll try to do as much of the boilerplate stuff I can for you, but
without being able to compile some backends myself it's hard to know
if I've broken anything. Parallel transactions is a potentially cool
feature that people have wanted for quite some time. We'll also
support full-threading (i.e. backend is fully threadsafe), and also
lazy-threading, where the backend can read stuff (perhaps) without a
lock, but need a lock for writing. And of course, the default is that
backends can only do one thing at a time, but this makes GUI's cry.

If you've got any questions, yell. Thanks.

Thanks,

Richard.