Yeah, there were a lot of side channels for sharing code that made merging things more difficult than they could have been. Poor discipline when devs were in a mad rush.

Seems to me that "sharing changes amongst your team members" is much more about process than it is about tools; and the process (whatever it is) must be followed by everyone every-time.

(With the benefit of hindsight) seems to me that many teams made their mistakes with vanilla Smalltalk and avoided those same mistakes when they moved to ENVY/Developer.

Envy enforced discipline in a way, which helped a lot. Sure, the devs could have had that discipline with filed out classes but because envy made sharing code easier, they inherited that process as well.