I completely indulged my most base and selfish urges this weekend and engaged in my true passion: writing Free Software, instead of doing all the Conservancy work that I should have been doing.
This all started because I simply wanted to have the aptitude command that caused the dpkg changes to appear in the etckeeper autocommit when running aptitude. Joey Hess confirms there's no way to get this info other than walking the process tree back up from the dpkg hooks calls, so the next best thing was closing the bug above so that I could at least past in the aptitude command myself into the commit log.
The patch only worked for Git because it's the only one of the VCS's that seemed to have a --edit/-e option, which forces editing of the commit message even if you've specified the commit message another way on the command line.
That led me to also write this patch for Mercurial that adds the --edit/-e option and submit a bug for Bazaar to add the same.
This all took me most of the weekend, which is insanely embarrassing. My hacking skills are, of course, quite weak these days. :-/