Well, if you consider a merge to be harakiri - then I agree it sounds frightening :)
If my work can not be ported after the merge, it is harakiri indeed (at least for me).
Why would it not portable? Are you using features that are totally unavailable in Pharo?
oh yes. well I don't know about "totally" unavailable, but I do try to maintain my code for as many images as possible and I can't get it to load in Pharo for non-trivial reasons that I currently don't even want to investigate any further. remember that Pharo explicitely does not attempt to keep backward compatibility, and it shows.
my codebase for muO is huge. I mean, huge. just download the archive in SqueakMap and see what's there, you'll have a better idea about what I'm talking about.
this is why I am at times speaking up on this list about backward compatibility: I would like (some) people to realize that, besides being a fun and toyish experimental programming environment very much open to improvement and radical change, Squeak is also a serious development platform upon which, year after year (I think I began with 2.7), actual work has been implemented that would be damaged or stuck in a dead-end if drastic changes with no concern about non-theoretical backward compatibility were to happen.
Stef