I want to bring back the `parent-pid` and `process-group` accessors as well as adding `session-id`. They don't fit well into my ProcessesCowan proposal, but they are harmless and trivial to implement.'
I am retracting this statement. They fit into ProcessesCowan well enough, now that I have the concept of a synthetic process object (one that is made either from a pid or directly for the current process). You cannot wait on a synthetic proc, but you can get its parent and get/set its process-group, session, etc.