I don't think we need complex rules here. Nor can people sign off things in advance.
I wasn't being clear. I don't mean rules, or formal sign-off. What I'm trying to capture is what sometimes currently happens in the patch queue, and is successful. There are (informal) agreements and commitments about process that allow us to break up a larger patch. A core committer says: the approach is looking good, it has a good chance of making it in if changes can be made. The individual or (better) group leading the change says: okay, we'll work on these changes, maybe in separate issues as suggested, and we'll do the followup that's needed. I see a couple of common weak points in this process, though. 1. Broken up pieces (separate patches) probably need a slightly different set of criteria, as they are steps toward a goal. We're not always clear about this. 2. Broken up pieces need a commitment to followup. As individuals or groups leading a change, we're often weak on followup. The immediate change gets in and we move on to something new and more exciting than cleanup. So, to work well, the "break it up into pieces" approach relies on informal agreements and commitments and trust from both the contributors and the core committers. The core committers need to go somewhat on faith, and the contributors need to follow through. Ideally, this is mapped out a bit in advance, there in the patch queue, so we know the game plan and what we're all committing to.